[pas]

Legally? It isn't really. (Your question was rhetorical, wasn't it?) Sure, maybe courts could separate these two issues on other grounds (such as using a side-channel for banning people based on the mere existence of an ad-blocker versus detecting the exact instance of blocking the ad from showing/playing somehow) - but from the point of the ToS, it's a clear deal. You get to access to YT but you have to watch ads. No ads, no YT.

That said, fuck that. It's not like people haven't been subverting ads for ages. (From the simple pause recording when the ad starts, rewind just a tad bit and resume-recording when the movie continues to Pi-Hole and Blockada on Android.)