I wonder if this is related to youtube being completely useless with firefox and ublock origin, sponsor block. It plays the ads just fine (and some of these ads are an hour long) but when it gets to the end it just stops.
It's directly related to YouTube getting a new CEO. According to some of the content creators I've watched they noticed an extreme change with ads essentially the moment he took over.
Same old story. New CEO needs to make shitty changes that will affect profits down the line after he uses his golden parachute prove himself worthy of a gigantic salary/bonus.