Possibly unfair to point the finger at RN here, but we found that the amount and complexity of code involved in developing using RN + JS + Redux was much higher than when just using Swift (< 50%). We've yet to repeat the experiment with Android/Kotlin, but I'm confident we'll get similar results.
As of late, the spit and polish for React Native on Android has been getting better, with some features even being exclusive to Android here and there. Though personally I am super interested in Fabric, if they really do make native calls as easy and performant as they say they will it will make RN dramatically closer to native platform development.