Hi there!
I've noticed that at some point in the past few weeks, the "search suggestions" have been greatly reduced or have completely disappeared. By "search suggestion" I mean when you start typing something in the search box and a list of possible completions appears below it. I've used them a lot to find notebooks or tags: just type in the first few letters and they would appear at the bottom of the search box, allowing me to do a quick filtered search.
Now instead, even if I type in the full, exact notebook title or tag (I did this as an experiment, though of course it defeats the purpose), no suggested filtered search appears.
IMHO, before experimenting with AI search, I'd make conventional search great again: let's not forget that super-powerful search is what made Evernote popular in the first place.