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.

For the last two days I haven't been able to watch youtube videos on Firefox without disabling uBlock.

Recently I've found Youtube to just show a white screen if it detects Firefox+uBO.