I’m not sure if the centralization is worse than the large portion of users on the large servers who joining copies of established communities on their own instances. Also, from my other reply:

It would force you to write a more descriptive name. Maybe we want to hide by community title and not the handle though.

Say you want to have a community for memes. It is terrible UX if you just see seven different “[email protected]” in the result. So with an opinionated search, you instead name your community Sopuli Memes, Solarpunk Memes, Programming Memes etc., or just Funny Memes Archive, and they would not be hidden.