diff --git a/babel.config.js b/babel.config.js
index 12d09a03c23b33..c826266bb05b1d 100644
--- a/babel.config.js
+++ b/babel.config.js
@@ -103,7 +103,7 @@ module.exports = function getBabelConfig(api) {
     ]);
   }
 
-  if (process.env.MUI_ADD_IMPORT_EXTENSIONS === 'true') {
+  if (!process.env.SKIP_CORE_EXPORTS_FORMAT) {
     plugins.push(['babel-plugin-add-import-extension', { extension: useESModules ? 'mjs' : 'js' }]);
   }
 
diff --git a/package.json b/package.json
index 17795c8bf039ef..04e53983a7c895 100644
--- a/package.json
+++ b/package.json
@@ -69,7 +69,7 @@
     "test:karma": "cross-env NODE_ENV=test karma start test/karma.conf.js",
     "test:karma:profile": "cross-env NODE_ENV=test karma start test/karma.conf.profile.js",
     "test:regressions": "cross-env NODE_ENV=production pnpm test:regressions:build && concurrently --success first --kill-others \"pnpm test:regressions:run\" \"pnpm test:regressions:server\"",
-    "test:regressions:build": "webpack --config test/regressions/webpack.config.js",
+    "test:regressions:build": "cross-env SKIP_CORE_EXPORTS_FORMAT=true webpack --config test/regressions/webpack.config.js",
     "test:regressions:dev": "concurrently \"pnpm test:regressions:build --watch\" \"pnpm test:regressions:server\"",
     "test:regressions:run": "mocha --config test/regressions/.mocharc.js --delay 'test/regressions/**/*.test.js'",
     "test:regressions:server": "serve test/regressions -p 5001",
diff --git a/packages/mui-core-downloads-tracker/package.json b/packages/mui-core-downloads-tracker/package.json
index cd2845f18da7b1..331c1d2b821ab4 100644
--- a/packages/mui-core-downloads-tracker/package.json
+++ b/packages/mui-core-downloads-tracker/package.json
@@ -21,7 +21,7 @@
   },
   "scripts": {
     "build": "mkdir build && pnpm build:copy-files",
-    "build:copy-files": "node ../../scripts/copyFiles.mjs --skipExportsField",
+    "build:copy-files": "cross-env SKIP_CORE_EXPORTS_FORMAT=true node ../../scripts/copyFiles.mjs",
     "prebuild": "rimraf build",
     "release": "pnpm build && pnpm publish"
   },
diff --git a/packages/mui-icons-material/package.json b/packages/mui-icons-material/package.json
index b79d44fcab79aa..252fa287b05455 100644
--- a/packages/mui-icons-material/package.json
+++ b/packages/mui-icons-material/package.json
@@ -33,9 +33,9 @@
     "build:lib:clean": "rimraf lib/ && pnpm build:lib",
     "build:legacy": "echo 'Skip legacy build'",
     "build:modern": "echo 'Skip modern build'",
-    "build:node": "node ../../scripts/build.mjs node --largeFiles --outDir lib",
-    "build:stable": "node ../../scripts/build.mjs stable --largeFiles --outDir lib",
-    "build:copy-files": "node ../../scripts/copyFiles.mjs --skipExportsField",
+    "build:node": "cross-env SKIP_CORE_EXPORTS_FORMAT=true node ../../scripts/build.mjs node --largeFiles --outDir lib",
+    "build:stable": "cross-env SKIP_CORE_EXPORTS_FORMAT=true node ../../scripts/build.mjs stable --largeFiles --outDir lib",
+    "build:copy-files": "cross-env SKIP_CORE_EXPORTS_FORMAT=true node ../../scripts/copyFiles.mjs",
     "build:typings": "node ./scripts/create-typings.mjs",
     "prebuild": "rimraf build",
     "release": "pnpm build && pnpm publish",
diff --git a/packages/mui-material/package.json b/packages/mui-material/package.json
index 29e2ce960aba0a..1445e8cfc691e6 100644
--- a/packages/mui-material/package.json
+++ b/packages/mui-material/package.json
@@ -32,7 +32,7 @@
     "build:modern": "node ../../scripts/build.mjs modern",
     "build:node": "node ../../scripts/build.mjs node",
     "build:stable": "node ../../scripts/build.mjs stable",
-    "build:umd": "cross-env BABEL_ENV=rollup rollup -c scripts/rollup.config.mjs",
+    "build:umd": "cross-env BABEL_ENV=rollup SKIP_CORE_EXPORTS_FORMAT=true rollup -c scripts/rollup.config.mjs",
     "build:copy-files": "node ../../scripts/copyFiles.mjs",
     "build:types": "node ../../scripts/buildTypes.mjs",
     "prebuild": "rimraf build tsconfig.build.tsbuildinfo",
diff --git a/scripts/build.mjs b/scripts/build.mjs
index c238e2c47f86a0..702a3642dc88c9 100644
--- a/scripts/build.mjs
+++ b/scripts/build.mjs
@@ -31,7 +31,6 @@ async function run(argv) {
     NODE_ENV: 'production',
     BABEL_ENV: bundle,
     MUI_BUILD_VERBOSE: verbose,
-    MUI_ADD_IMPORT_EXTENSIONS: true,
   };
   const babelConfigPath = path.resolve(getWorkspaceRoot(), 'babel.config.js');
   const srcDir = path.resolve('./src');
@@ -70,8 +69,6 @@ async function run(argv) {
     }[bundle],
   );
 
-  const outExtension = bundle === 'node' ? '.js' : '.mjs';
-
   const babelArgs = [
     '--config-file',
     babelConfigPath,
@@ -80,8 +77,6 @@ async function run(argv) {
     srcDir,
     '--out-dir',
     outDir,
-    '--out-file-extension',
-    outExtension,
     '--ignore',
     // Need to put these patterns in quotes otherwise they might be evaluated by the used terminal.
     `"${ignore.join('","')}"`,
@@ -90,6 +85,11 @@ async function run(argv) {
     babelArgs.push('--compact false');
   }
 
+  if (!process.env.SKIP_CORE_EXPORTS_FORMAT) {
+    const outExtension = bundle === 'node' ? '.js' : `.mjs`;
+    babelArgs.push('--out-file-extension', outExtension);
+  }
+
   const command = ['pnpm babel', ...babelArgs].join(' ');
 
   if (verbose) {
diff --git a/scripts/copyFiles.mjs b/scripts/copyFiles.mjs
index 418840604e70be..dbe3e29a7ca49f 100644
--- a/scripts/copyFiles.mjs
+++ b/scripts/copyFiles.mjs
@@ -1,6 +1,5 @@
 /* eslint-disable no-console */
 import path from 'path';
-import yargs from 'yargs';
 import {
   createModulePackages,
   createPackageFile,
@@ -14,6 +13,7 @@ const buildPath = path.join(packagePath, './build');
 const srcPath = path.join(packagePath, './src');
 
 async function addLicense(packageData) {
+  const esmExtension = process.env.SKIP_CORE_EXPORTS_FORMAT ? 'js' : 'mjs';
   const license = `/**
  * ${packageData.name} v${packageData.version}
  *
@@ -24,9 +24,9 @@ async function addLicense(packageData) {
 `;
   await Promise.all(
     [
-      './index.mjs',
-      './legacy/index.mjs',
-      './modern/index.mjs',
+      `./index.${esmExtension}`,
+      `./legacy/index.${esmExtension}`,
+      `./modern/index.${esmExtension}`,
       './node/index.js',
       './umd/material-ui.development.js',
       './umd/material-ui.production.min.js',
@@ -44,14 +44,14 @@ async function addLicense(packageData) {
   );
 }
 
-async function run(argv) {
-  const { extraFiles, skipExportsField } = argv;
+async function run() {
+  const extraFiles = process.argv.slice(2);
 
   try {
     // TypeScript
     await typescriptCopy({ from: srcPath, to: buildPath });
 
-    const packageData = await createPackageFile(skipExportsField);
+    const packageData = await createPackageFile();
 
     await Promise.all(
       ['./README.md', '../../CHANGELOG.md', '../../LICENSE', ...extraFiles].map(async (file) => {
@@ -69,26 +69,4 @@ async function run(argv) {
   }
 }
 
-yargs(process.argv.slice(2))
-  .command({
-    command: '$0 [extraFiles..]',
-    description: 'copy files',
-    builder: (command) => {
-      return command
-        .positional('extraFiles', {
-          type: 'array',
-          default: [],
-        })
-        .option('skipExportsField', {
-          type: 'boolean',
-          default: false,
-          describe:
-            'Set to `true` if you wish to skip adding the exports field. Adding the exports field is only supported for top level ESM packages.',
-        });
-    },
-    handler: run,
-  })
-  .help()
-  .strict(true)
-  .version(false)
-  .parse();
+run();
diff --git a/scripts/copyFilesUtils.mjs b/scripts/copyFilesUtils.mjs
index b6e5c5a3d6cb77..41636a97b33dbe 100644
--- a/scripts/copyFilesUtils.mjs
+++ b/scripts/copyFilesUtils.mjs
@@ -33,6 +33,7 @@ export async function includeFileInBuild(file, target = path.basename(file)) {
  * @param {string} param0.to
  */
 export async function createModulePackages({ from, to }) {
+  const esmExtension = process.env.SKIP_CORE_EXPORTS_FORMAT ? 'js' : 'mjs';
   const directoryPackages = glob.sync('*/index.{js,ts,tsx}', { cwd: from }).map(path.dirname);
 
   await Promise.all(
@@ -45,8 +46,8 @@ export async function createModulePackages({ from, to }) {
       const packageJson = {
         sideEffects: false,
         module: topLevelPathImportsAreCommonJSModules
-          ? path.posix.join('../esm', directoryPackage, 'index.mjs')
-          : './index.mjs',
+          ? path.posix.join('../esm', directoryPackage, `index.${esmExtension}`)
+          : `./index.${esmExtension}`,
         main: topLevelPathImportsAreCommonJSModules
           ? './index.js'
           : path.posix.join('../node', directoryPackage, 'index.js'),
@@ -91,12 +92,43 @@ export async function typescriptCopy({ from, to }) {
   return Promise.all(cmds);
 }
 
+/**
+ * Returns the Core exports field.
+ * @returns {object}
+ */
+function getCoreExportsField() {
+  const coreExportsField = {};
+
+    const hasIndexMjs = fse.existsSync(path.resolve(buildPath, './index.mjs'));
+    if (hasIndexMjs) {
+      // Asumes the types file and node build are set up correctly
+      coreExportsField['.'] = {
+        types: './index.d.ts',
+        import: './index.mjs',
+        default: './node/index.js',
+      };
+    }
+
+    const hasNestedIndexFiles = glob.sync('*/index.mjs', { cwd: buildPath }).length > 0;
+    if (hasNestedIndexFiles) {
+      // Asumes the types files and node build are set up correctly
+      coreExportsField['./*'] = {
+        types: './*/index.d.ts',
+        import: './*/index.mjs',
+        default: './node/*/index.js',
+      };
+    }
+
+    return coreExportsField;
+}
+
 /**
  * Creates a package.json in the build directory.
  * @param {boolean} skipExportsField Whether to skip the exports field in the package.json. Only top level ESM packages are supported.
  * @returns {Promise<object>}
  */
-export async function createPackageFile(skipExportsField = false) {
+export async function createPackageFile() {
+  const esmExtension = process.env.SKIP_CORE_EXPORTS_FORMAT ? 'js' : 'mjs';
   const packageData = await fse.readFile(path.resolve(packagePath, './package.json'), 'utf8');
   const { nyc, scripts, devDependencies, workspaces, ...packageDataOther } =
     JSON.parse(packageData);
@@ -109,9 +141,9 @@ export async function createPackageFile(skipExportsField = false) {
           main: fse.existsSync(path.resolve(buildPath, './node/index.js'))
             ? './node/index.js'
             : './index.js',
-          module: fse.existsSync(path.resolve(buildPath, './esm/index.mjs'))
-            ? './esm/index.mjs'
-            : './index.mjs',
+          module: fse.existsSync(path.resolve(buildPath, `./esm/index.${esmExtension}`))
+            ? `./esm/index.${esmExtension}`
+            : `./index.${esmExtension}`,
         }
       : {}),
   };
@@ -121,32 +153,10 @@ export async function createPackageFile(skipExportsField = false) {
     newPackageData.types = './index.d.ts';
   }
 
-  if (!skipExportsField) {
-    const addedExports = {};
-
-    const hasIndexMjs = fse.existsSync(path.resolve(buildPath, './index.mjs'));
-    if (hasIndexMjs) {
-      // Asumes the types file and node build are set up correctly
-      addedExports['.'] = {
-        types: './index.d.ts',
-        import: './index.mjs',
-        default: './node/index.js',
-      };
-    }
-
-    const hasNestedIndexFiles = glob.sync('*/index.mjs', { cwd: buildPath }).length > 0;
-    if (hasNestedIndexFiles) {
-      // Asumes the types files and node build are set up correctly
-      addedExports['./*'] = {
-        types: './*/index.d.ts',
-        import: './*/index.mjs',
-        default: './node/*/index.js',
-      };
-    }
-
+  if (!process.env.SKIP_CORE_EXPORTS_FORMAT) {
     newPackageData.exports = {
       ...packageDataOther.exports,
-      ...addedExports,
+      ...getCoreExportsField(),
     };
   }