Those ad-blocked viewers are important, which is why YT doesn't actually crack down on them.

Those are the people who will happily go to an alternative product. And while that product might start as a pirate YouTube, the one that nabs 30% of YT's traffic can certainly make a pivot to legit. If you're a content creator whose audience is mostly in that group, you're likely to start posting content directly on the competitor's site.

I'm guessing OP had their account banned for using a tool like yt-dl too aggressively. Then again, doing that does give a warning.