Yeah, that's what I have been wondering all the time, people claiming that Adblockers stopped working, now people are developing new extensions/blockers, but here I am, playing YouTube without ads like before, with nothing more than uBlock Origin....
It gave me the warning with uBlock origin a few weeks ago. I think the ad-detection is not turned on for all, that's why it may seem it still works. It also could be that some of the filters in uBlock trigger the detection more than others.