The not interested button doesn't really work for me, it just blocks that particular video but other videos in that category still show up no matter what.
The “Don’t recommend channel” button also doesn’t really work for me. It used to work, but now the channels keep coming back. YouTube has been trying to get me to watch videos from “Dr.” Sten Ekberg. After watching one video a couple years ago I quickly realised he’s full of shit. I’ve clicked the “Don’t suggest channel” button so many times, but after a short while his videos return to my feed.