The customizability specifically is key for a lot of people. I maintain an Atom package for finding and opening files by path in a similar way to Emacs' find-file, and at this point I can't really go back to not having something similar. I tried looking into how I'd implement a similar interface in VSCode and couldn't find any UI primitives that would have worked.

There's a definite performance cost for this customizability, but I'm willing to pay for it.