I've found a curious variety of AI videos: releases of motorbikes that don't exist, brought by Youtube algorithm. I guess the point is just clicks or ads money. Some comments, by bots or gullible users.
No longer seen recently, not sure it's because YT's crackdown or me repeteadly clicking "not recommend me this channel" (there're a handful)
From what I've seen YT takes "Don't show me this channel again" very seriously but the effect appears to be limited just to you. It would be very silly for YT to fail to enforce that preference as a user who is willing to go through an annoyingly multi-step flow to express their displeasure is on who would never monetarily engage in the content anyways - but neither it (nor the reporting system) seem to have a significant impact on the visibility of that content to others since both are often used for brigading or personal preference.