But the main thing missing isn't video-by-video like/dislike.

The thing that's missing is something like a control panel. It would show "these are topics/tags I'm especially interested in", "these are topics/tags I want to avoid entirely", "these are things to show occasionally" "show topics similar to what I'm current watch" or not.

All "but they have that objections" here seem very around "but it does have ways to give the opaque recommender suggestions" - yes, but how the recommender works is still unknown, "magical", opaque and how the suggestions will effect the recommender is also unknown.

I mean, I happen to know the only way the only affect the recommender is to actually remove items from your history. That's pretty klunky. And it makes it impossible to say "give me X but not Y kind of X"

The issue with the "Not interested/Don't recommend channel" is that it's the nuclear option. It does make content go away, but more often than not, what I really want is just to watch something else right now. The content might be perfectly fine and up to my taste, but when Youtube keeps recommending the same stuff again and again, there is no easy way to just reduce that a little without nuking it completely.