AND you’re assuming youtube wants to continue the already unsustainable ad-based model at all
No, I was explaining how people who do not watch ads are still valuable to YouTube today. It doesn't matter if they want to move away from serving ads in the future or not, the points above are still valid.
Netflix is actually a great parallel. They need people to watch the shows and buzz about them to draw in more subscribers. YouTube is the same way, they need people sharing videos and funny comments to scrape attention away from other bits of entertainment.
Further, this isn't a binary outcome. Each time YouTube makes it a little harder to block ads, a slice of people who don't want to put in the effort will start watching them. It is trivial, on the software side, to fully block a video from playing if the ad is not served. To date, they have not done that, and I sincerely doubt they ever will - because ad-free viewers are still valuable.
Yes, they would prefer if everyone watched ads. But they would still prefer ad-free viewers to watch YouTube and add to the network effect than to spend their time elsewhere.