React has certain weaknesses that aren’t seen in other UI libraries/frameworks as well - forms are a complete mess to work with, even with formik, and animations are pretty problematic.
As with anything, there are tradeoffs to approaches. FB isn’t as form heavy in general, so optimizing how it works for the rendering inputs from external sources & dev usability makes sense for their use cases. It’s important not to conflate this by overpraising.