These kind of libraries are always easy to spot in the wild because of their transitions on things like modals and action sheets don’t match native. They’re just not as smooth.
I mean personally I think any developer worth their salt should be able to learn native development, and any company that wants to make a good app should hire and invest in native developers / development. But that's a hard sell these days.
That said I’m inclined to agree - emulating system controls with CSS always feels very uncanny valley to me.