Maybe I can simplify it for you with this question:
Does Google have the ability to legally compel you to only use chrome?
Im guessing you would say no- Antitrust and whatnot. So the next followup is, Does Google have the ability to tell blind people they cannot use screen readers? Or that people on linux cant browse the site in lynx?
Again, I am guessing the answer is no- Theres anti competitive, antitrust and 230c reasons why. Legally, ad blocking is fine to do. Heres a great article going over it : https://scholarlycommons.law.wlu.edu/cgi/viewcontent.cgi?art...
HOWEVER- I disagree with the premise that Youtube cant try to stop adblockers- They just need to do so in a way that doesnt target specifically target a user. Twitch did a system where they would not send the video stream to you until the advertisement was done playing (which was embedded in the feed itself)- So if you blocked the ad somehow, you would just look at a black screen for 15-30 seconds. This, in my opinion would be completely compliant.