They could aggregate logs and figure out who is not downloading ad video. But yes, it is a cat and mouse game, because the pirates will attempt do what it takes to fool the detections.
But content on YouTube is subscription and ad free or with ads. To subvert that is generally labeled piracy.
YouTube does have drop a prop function to a creator which be another way to more directly direct money to creators of content you consume. If you do $5 one out of 1k videos you watch I thik it's fair to skip ads :)