You can write a CRUD like app without any hardware/native code required. However, even when you do need that code - for example I'm building an app that records and plays audio - react native still gives you an advantage in the sense that you only need to expose a hardware API but all the logic still stays in javascript. I've managed to write just enough Objective C and Java to expose some APIs I need, and no more.

There is also a lot of react-native npm packages that abstract away the hardware issues, quality & completeness varies however.