The question is mostly nonsensical. Create-React-App is an abstraction over a prebuilt Webpack+Babel config, with a bunch of niceties for developer experience like an in-page error overlay, linting for common mistakes, and so on. The template it uses for a new app adds React and ReactDOM to your dependencies, and imports React into the couple starting files, but it's entirely up to you what you do with the project's contents after that. If you want to delete any references to React and use Preact instead, you can. In fact, you could probably go start using Mithril or Vue or something else if you really wanted to.