I don't use a lot of apps. The ones I do are "not optional" (like my banking app etc.)

Frankly, I couldn't care less about the UI looks or whether it's native or whatever. I get in, perform a task, get out.

As long as I can do what I need to do, the buttons can be anything.

I think developers care deeply about this. I think if you're in a competitive space then it matters. But I don't think Joe Public cares in the slightest.

Performance yes. Usability yes. Ability to quickly do what I want, yes. Whether it uses native check boxes or owner-drawn check boxes? Nobody cares (for some definition of nobody. )

Put another way, Usability is important. Yes it should look "nice". But at this point I probably don't know what the 'native UI' looks like. Nor do I care.