face it, the youtube offering is just kinda shitty. its like with piracy of music, movies and such, it is a distribution problem. Does it make it legal in the case of music/movies? probably not. Is it legal to adblock? in most places, yes.

could one make an argument of it not being morally justified? maybe.

does youtube, in the way google/alphabet wants to run it suck? most definitely. Is it possible to easily work around some of the biggest stuff here? yes.

well this is what a great many people choose to do, and youtube had better accept reality and deal with it. If they make it impossible to block ads, that is probably within their rights (assuming they implement some technical solution themselves), but that will come with some consequences