Earlier quoted context omitted.
I use Firefox with uBlock and besides a couple of times where video start was delayed by a few seconds it has been working as well as before.
Google does A/B testing for anti ad blockers. Not only do I get slowdowns and some videos don't load at all at times, but I also get a notification that explains that the reason is using adblockers.
Though it’s mostly good for my addiction since it makes me use youtube less.