This is already quite easy to do technologically, it's mostly a question of at what point Google feels it's worth doing, since once they start they have to commit to closing whatever exploits people find. And deal with the fallout of blocking a bunch of people on random old devices that weren't blocking ads anyway.

Of course people can still work around by running modified apps on rooted devices but it'll be enough to defeat a probably fairly large slice of users too lazy to jump through hoops - and as a bonus it won't just block Revanced (which is a fair bit of work to get running already) but also the other apps for media players like Smarttube, which were easier for people to set up.

And finally when all else fails they will spend the compute to embed the ads in the video stream, once they work out how to minimize the distribution costs for that.

Rerevanced

I remeber the girls at school listening to bootlegged YouTube videos from shitty rip off apps from the appstore

That could have been yesterday or like 15 years ago