Edit: I’m really sorry I just noticed that you posted this MONTHS ago. I’m an idiot
A lot of people watch videos on their phones, and ad-blocking is a lot more of a pain there. The official YouTube app is pretty much the only app on iOS that I know of and no ad-blocker works for that, I don’t think - though a good ad-blocker and Safari works quite well to watch YouTube on iPhone.
No real options on Apple TV though, that I know of.