I think it's both - Boosts now represent pretty much all the 'Chosen for you' part of the feed through active promotion above street level, while there is such a volume of AI crap that it is clogging the lower sewers of the algorithm like a fatberg.
It's simply not worth posting here right now, and anything I might want to reuse in the future, on another platform or for inclusion in an ebook, is not safe here either.
RIP Medium? They say they will make a profit this year, but from what? Skimming the house take off the top of an AI word soup casino?