Repository: create-react-app
Issue: babel-preset-react-app no longer generates ES modules with babel CLI
Labels: needs triage,issue: bug report

### Describe the bug

Hi team, we used create-react-app v3.4 with [react-styleguidist](https://github.com/styleguidist/react-styleguidist) v11 as part of our internal component library project. To build the actual library distribution we use babel CLI with the react-app preset, and this normally generated ES5 files with ES6 module syntax, which allowed the library and its transitive dependencies to be treeshaken in the consuming web application (which is also built with CRA and thus bundled with webpack).

However, since updating to react-scripts v4.0.1 the `react-app` preset has stopped generating ES6 modules, and now generates CJS modules. This change broke treeshaking in the consuming app and blew out our bundle size, but also resulted in a production defect because we were using a handful of modules from [react-use](https://github.com/streamich/react-use) in the component library, but when tree-shaking broke we ended up pulling in the entire library, included the `useLocation()` module (which [required a polyfill](https://github.com/streamich/react-use/issues/73) for `window.Event`) and this broke the app for IE11 users.

It seems [this bugfix](https://github.com/streamich/react-use/issues/73) was the root cause of the ES6 module change. There also doesn't seem to be any configuration options available to restoring the legacy behaviour.

### Did you try recovering your dependencies?

N/A?

### Which terms did you search for in User Guide?

N/A?

### Environment
```
Environment Info:

  current version of create-react-app: 4.0.3
  running from /Users/Kris_Dover/.npm/_npx/41472/lib/node_modules/create-react-app

  System:
    OS: macOS 11.2
    CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
  Binaries:
    Node: 12.14.0 - ~/.nvm/versions/node/v12.14.0/bin/node
    Yarn: 1.22.10 - ~/.nvm/versions/node/v12.14.0/bin/yarn
    npm: 6.13.4 - ~/.nvm/versions/node/v12.14.0/bin/npm
  Browsers:
    Chrome: 88.0.4324.192
    Edge: Not Found
    Firefox: 85.0.2
    Safari: 14.0.3
  npmPackages:
    react: 17.0.1 => 17.0.1 
    react-dom: 17.0.1 => 17.0.1 
    react-scripts: 4.0.3 => 4.0.3 
  npmGlobalPackages:
    create-react-app: Not Found
```

### Steps to reproduce

<!--
  How would you describe your issue to someone who doesn’t know you or your project?
  Try to write a sequence of steps that anybody can repeat to see the issue.
-->

(Write your steps here:)

1. `npx create-react-app my-componet-library`
2. `cd my-component-library && npm install -S @babel/cli @babel/core`
3.  Add the following config to `package.json`:
```
 "babel": {
        "presets": [
            [
                "react-app",
                {
                    "absoluteRuntime": false
                }
            ]
        ]
    }
```
4. `NODE_ENV=production npx babel --extensions '.tsx,.ts,.js,.jsx' ./src --out-dir ./dist --copy-files --no-copy-ignored`

### Expected behavior

`dist/App.js` should have ES6 module syntax e.g.

```
...
export default App;
```

### Actual behavior

`dist/App.js` has CJS module syntax:

```
...
var _default = App;
exports.default = _default;
```

### Reproducible demo

`git clone https://github.com/krisdover/cra-react-app-preset-issue-example`
`cd cra-react-app-preset-issue-example`
`npm run build:lib`