Pretty sure it's caused by the algorithm not serving the user anymore... Unless I block a channel forever I only get served the same channels over and over or it's an endless reel of ai slop with that dead crappy voice on all kinds of variations...
And lately they're starting to get more malicious: https://www.youtube.com/watch?v=UaHW24jOYVw
And I'm quite deliberate with avoiding ragebait and slop, and I remove stuff from my watch history if I get duped etc.
That said, I have noticed a trend amongst the creators I've subscribed to that the average video length has gone up. This has been a longer term trend, but many who used to do 30-40 min videos now often to 1-1.5 hr videos.
I've heard YouTube punishes people quitting a video midway, so perhaps there's something going on there too. At least for myself I often have to watch these videos over multiple sessions, and chances are there that I just forget and move on.
So perhaps some compounding factors making things worse.