Adding more abstractions on top will not significantly improve the fact that you are at the whims and mercy of companies that don’t care about you, so I don’t see RN as an improvement.
If you want to avoid vendor lockin, don’t do mobile apps, go to web. Then, you can also just switch RN to React simply or any other framework.
With native mobile dev, lock-in is less of a problem career-wise, because it's a duopoly, so your chosen technology is unlikely to become unfashionable like it would if you were specialised in a particular web framework.
So if they're learning the native frameworks anyway, they may as well use them. These days with Swift and Kotlin most logic code transfers pretty cleanly and most apps can be LEGO'd together from UIKit/SwiftUI/Compose components, so the workload isn't as high as one might expect.
Aside from that, early on it's usually better to start with one platform, nail the UI and interaction, and then once the app is proven worry about the other platform.
RN libraries are so often buggy and disappointing in my experience.
That would apply more to React Native since you are stuck with its vendored abstractions and you can't just swap out React Native once you've built with it.
I think you're commenting on how iOS development is a less portable skill than a toolkit than runs on all platforms. Or that your iOS app is stuck on one platform. That is certainly true. But don't overlook the value of expertise in a native platform instead of just one set of abstractions that run on top of it. There are things you can do on the native platform, like optimizing performance, that you can't do using something like React Native.
It's all just trade-offs.
This applies to the web, too. A dev who has a good grasp of of the fundamentals (HTML, CSS, JS), the DOM, what does and doesn't trigger a repaint, etc is going to be able to take a React project a lot further than a dev who only knows how to use React.