> a compelling reason to use a ubiquitous framework is that the ubiquity means folks intuitively know how to interact with your product

Not that I disagree with you, but I'll also offer a tradeoff.

When people expect to pick up your app intuitively, it can also just mean them using the app absent-mindedly, which can mean them skipping the manual and jumping straight to trying to tie up the support lines. Whereas if your ui asks for a user's full focus up front, yes there are downsides to that but they're also more engaged.