Who told you that? You can write entire C libraries and call them from Electron just fine. Browser is a native application after all. All this "native applications" debate boils down to the UI implementation strategy. Maintaining three separate UI stacks (WinUI, SwiftUI, GTK/Qt) is dramatically more expensive and slower to iterate on than a single web-based UI with shared logic
We already have three major OSes, all doing things differently. The browsers, on the other hand, use the same language, same rendering model, same layout system, and same accessibility layer everywhere, which is a massive abstraction win.
You don't casually give up massive abstraction wins just to say "it's native". If "just build it natively" were actually easier, faster, or cheaper at scale, everyone would do just that.
It's weird that we don't have a unified "React Native Desktop" that would build upon the react-native-windows package and add similar backends for MacOS and Linux. That way we could be building native apps while keeping the stuff developers like from React.
So if you want a multiplatform desktop app also supporting Linux, React Native isn't going to cut it.
React Native Skia allegedly runs on Linux too