They started blocking people who use ad blockers from watching videos if they don't disable it on YouTube. I think they just started doing it in the last few weeks
I have had no issues. Even if they did end up successfully blocking (not likely) the videos are accessible via 3rd party sites/clients. I don’t see Google ever being able to successfully block users without adding a login requirement, and even then…
I don't think Google ever blocked someone for abusing their services (unless it was GCP, which is not meant for personal use anyway), they believe in annoying a person to compliance instead of banning them.