React Native likley has a productivity benefit for simpler interfaces -- the framework is less complex and it's faster to get started. By contrast, iOS frameworks are very powerful and enable you to do a lot more.

However, a lot of this catches up to you.

1) iOS/Android already have very sophisticated and powerful MVC layers, which is what React brings to the web.

2) React Native is not performant and it's hard to solve these performance problems. I've heard a lot of people say this doesn't matter, but I've noticed this is usually said by those who are doing mobile apps for the first time coming from the desktop/browser world where problems can be hidden easier. On mobile you have no such affordances and performance issues are a bigger big deal. Funny enough, React Native would actually perform better (e.g. with scrolling) if it used a shadow view layer like its web counterpart uses. Check out https://texturegroup.org/ for an example of how this would work.