Huh, really? I just tried on a fresh browser (Safari on macOS) and didn't get any kind of popup. I never use Safari, so it's safe to say I've never accessed YT on it. I have no extensions, I was just presented with a page that says "search to get started" or something, then when I load a video, I get ads. No TOS popup at all.
So me adding an ad-blocker in this scenario wouldn't be an issue because I was never asked to accept any terms of service. At least that's my understanding. And it certainly wouldn't be piracy because I'm doing nothing to access something I shouldn't, YouTube is just giving me access because I asked nicely.
