I would guess about two thirds of the channels I consistently watch I originally discovered through algorithm recommendations. I think it works extremely well.
For me, probably 90% of what I watch I'm not interested in and often I'm repelled by. This is because I mostly watch to find out what things I'm not familiar with are.
For example let's say I'm a liberal. I'm not going to watch liberal political videos because I know generally what they're going to say and I don't need my political views stroked in order to be happy. But I will watch various other political videos, no matter how extreme or not, so I can be at least a little familiar with their behaviour and views.
YT can't cope with this. To their systems I seem to be randomly picking videos with no correlation with the subject matter or other users and no reinforcing pattern. It just gives up and recommends things based on the behaviour of the general population, as if they had no data on me at all.
Every day, averaging 2-3 hours. It's background for working and foreground for evening viewing.
If that's "cutting edge ML", then going off my YouTube recommendations, we're back in another AI winter. If I watch one video from a channel I've not seen before, I'll get that channel recommended constantly even if it bears no resemblance to what I normally watch. On my Explore page, the first 22 videos (of which 8 are Fortnite-related!) hold no interest for me. My Home page is just channels I've watched repeatedly and/or am subscribed to. It's a mess.