I'm reading
The Age of AI whose authors include Eric Schmidt. There is a part where they mention that in 2015 Google moved from "human developed" search algos to "Machine Learning". I don't know what that means in practical terms, but when I saw it a light went on for why their search had become so bad.
I'd just add that I think it's bad in the sense that many others have mentioned- lots of crap at the top, ads, very hard to find more obscure stuff. Otoh, I generally still find it better than bing / ddg for most mainstream searches I would do.