True, but it is reusing an (alien) middleware on top of that. I like react-native and have used it, but a <Text>, <View>, or <ScrollView> isn't the same thing as directly using the native widget APIs yourself, or using the native tooling like Android XML files, XIBs, etc. There's a class of apps where you really need the direct access, and currently for React-Native, that means writing native modules and tying them to markup, which invariably leads to people trying to create versions that work on Android and iOS unified by a single <Element>.

React-Native works, apps like Discord prove that. But Gmail and Docs tried the approach of running their huge apps business logic 100% in JS on mobile, and the performance and memory usage didn't meet expectations. If you try to do something like run formula recalculations on a 20,000 cell spreadsheet, on a low powered Android device, the performance is much worse than running the same code in Dalvik/ART.