Don't know anything about your company or product, but I've been in 4 different companies where React was used. Every single one had different setup, best practices, state management lib, "the way" of doing things, bundler (create-react-app, next.js), etc.

Each project was so big, that I'm little in doubt about your statement "within 24h they contribute to the code". It could be your react apps are very very small or junior devs are very very good and probably shouldn't be called juniors.