Hell yes. I love the idea. It's just that frameworks beat them to the punch of mass adoption.

IMO, 80% of the neat things on the web could easily be made into components, closed or not (preferably closed DOM, fuck you if you need to fiddle with everything outside of what you deliver).

For an easy example: Embedding PeerTube videos just as easily as YouTube videos in random web pages. Even if that is presently possible (and it is), I haven't seen it out there in the wild.