I have had reasonable success with Youtube's built-in algorithm-massaging features. It mostly always respects "Do Not Recommend Channel", and understands "Not Interested" after a couple repetitions.
That doesn’t work as well for stuff that you wish other people would find noxious but they don’t: neo-Nazis probably would rather see more neo-Nazi things rather than fewer, even if the broader social consensus is (at least on the pages of the New York Times) that those things fall under the uselessly vague header of “toxic.”
Even if the recommenders only filter out some of what you want less of, ditching them entirely means you’ll see more of the portion of the slop that they’re deprioritizing the way you want them to.
No, they're incentivized to increase the amount of content advertisers find acceptable.
Plus, youtube isn't strictly watching, many people do make a living from the platform and these algorithmic controls are not available to them in any way at all.
> ditching them entirely
Which is why I implied that user oriented control is the factor to care about. Nowhere did I suggest you had to do this, just remove _corporate_ control of that list.