[scarface74]

After all, Java is compiled to byte code and powers plenty of high traffic servers efficiently.

How well has Java done on the client in the last two decades?

Many AAA games use ActionScript, Python, Lua, etc for their UIs and scripting for mods.

What's the actual performance sensitive parts written in?

[ascorbic]

I don't think anyone is suggesting writing game engines or the core of graphics processors or video renderers in React Native. It's for the frontend. The pattern of using React Native for the frontend and native moduels for the backend is a pattern being used by many companies. The difficult stuff can be written as a native cross platform library, while the front end can use React Native. This is what MS is doing with Office.