A chat app is one of those relatively few cases where React makes some sense.

But, React is easy and intuitive to use for the use case that makes the least sense. Once you get to complex state, I'd argue that React doesn't help much. There are a lot of different tools and ways to manage state, but the way React takes over rendering often leads to weird and confusing bugs, as the 'declarative' syntax is a *very* leaky abstraction.