What I don't understand is why they can't use AI to improve search quality. I'm sure there are tons of reasons, like institutional paralysis, but from an outside perspective it's frustrating because I'd be happy with search that just works.

I use ChatGPT these days largely as a better search. Where Google is flooded with junk, ChatGPT usually answers my question straightforwardly. If it's something important to me, I'll go back to Google to verify that the answer I got wasn't a pure hallucination, and that's usually pretty easy to do now that I have the key details I was missing before.