They have ruined recommendations, too, a long time ago. They ruined search, too. If you search for something, it will give you maybe 5 results at best, and as you scroll down, the rest is totally unrelated to the searched term. YouTube has been ruined a long time ago.
Because you have not pressed “do not recommend channel”. That is the best youtube feature.
You should know that do not recommend channel has never really worked. Especially if there are any videos from that channel in your history.... ever.
It's very annoying if I do want to see that channel, just not THAT video. You also have to be careful with that button because there's no way to selectively unblock channels. There's a feature to undo your entire Do Not Recommend / Not Interested history but not to undo it for an individual channel / video.