I use Youtube every day and find the recommendation engine extremely predictable. Whatever video(s) I've watched recently all the way through seem to dominate the recommendations. Which on the surface seems logical, but sometimes I watched a video and at the end decided I didn't really like it. I end up having to do a LOT of "Not interested" -> "I don't like this channel" / "I don't like this video" to clear them out.

I wish the recommendation engine had a better idea of what I liked based on the fact that I've been using Youtube for years, and I've thumbs-upped a lot of videos, and told it a lot of channels and videos that I don't like. But maybe that's just asking too much?