I still hold the opinion that they could absolutely block you out. I use uBlock Origin and there was actually a time where I got blocked/warnings every day. Even with upgrading my plugin / refreshing all block lists.
At some point I finally gave in and grabbed YouTube Premium, not because of the ads (I’d rather stop watching than watch with ads), but because I needed their music service (Used Amazon Music before, the app sucked. Music quality was the highest out there though. Also cancelled Prime for a double whammy).
For example the moment an ad gets triggered they could just refuse to send you video data. And if the ad is an unskipable 15 seconds, block playback for 15 seconds. Done. Even if you block this, you get 15 seconds of nothing and will soon be pissed off enough to either start watching ads, buy Premium or leave (no longer costing them bandwidth).