Xamarin is given as an example of a better alternative why exactly? You develop a single layout in React Native, while in Xamarin you just share the C# code, so

Xamarin is given as an example of a better alternative why exactly? You develop a single layout in React Native, while in Xamarin you just share the C# code, so separate platforms need separate UI code (unless you want to rely on their weak Xamarin.Forms API), and at that point you can just write common code in C or C++ and not rely on any third party. It's hardly comparable.