I did an experiment where I really invested in my YouTube suggestions, and you can definitely groom your recommendations, and then they can be pretty good. But then you have an issue where you get into a new hobby or a new interest, and so you watch some videos attributed to that, your recommendations spiral back out of control. So you can do a whole bunch of grooming work, but probably they just go back to being like 80% wrong. I got vaguely interested in the piano, and now 80% of my recommendations are music related, but not actually things I care about, and they've just gone back to being total trash.