It seems part of the problem is, obviously, Youtube themselves arbitrarily fucking over creators regularly with no transparency or communication, and basically arbitrarily dictating what can and can't make money, and fucking around with how subscriptions work. Granted, more people should really just be checking their subscriptions page, that's significantly more reliable than just the front page. I rarely go to the front page anymore. But obviously a big part of the problem is Youtube regularly fucking over everyone for no apparent reason and making certain types of content creators less viable. If you make short videos less than ten minutes long, Youtube fucks you over. If you're an independent creator that isn't already very popular, Youtube is not interested in providing you revenue.
Of course, the other half is there being way too many lets play channels now. And like most forms of entertainment that are numerous, most of them are trash.