Example of native modules with React Native wrappers: https://facebook.github.io/react-native/docs/components-and-...
NativeModules API: https://facebook.github.io/react-native/docs/native-modules-...
Also, the security and performance implications of the Javascript dependency ecosystem should not be ignored.
Small greenfield app on a shoestring budget? It's perfect for that.
Although much as it pains me, I think that is a lost cause. And it was lost through attrition - devs kept throwing non-native (often, JS-based) apps at users, and users got conditioned to each app having its own look, much like websites.
Fortunately, it does seem like these platforms are beginning to converge on a set of common UI patterns, e.g. Android adopting the tab bar, and iOS apps beginning to adopt Android's horizontal-paging navigation. The colors, iconography, and typography shifting can disorient somewhat, but I'd argue it's the navigation model that's most disruptive when using different apps.
My comment was that it doesn't preclude it, addressing the parent's conflation of language and view layer.
Yes, you might have to do more work in React Native. But similar frameworks[1] appear to do this out of the box, if that helps.