SAO is sort of a confluence of everything that could possibly merge together and form a massive hate bandwagon.
It's bad, but not so bad that it can't get popular by being aimed at a demographic that isn't exactly known for being smart or having ultra-patrician tastes (teenage boys), it was massively popular, and at a time when anime was getting way more popular, and this is even more apparent now, but its popularity had a very negative effect on the industry with dozens of new shows every season, each trying to be the "new" SAO and all ending up even worse.
It also happened at a time when the "angry internet reviewer" genre was receiving a second peak on youtube, and the algorithm heavily favored those types of videos. Largely, I think the shtick was popular because your average normalfag, no matter how much they dislike it on the inside, will never openly criticize brand/product unless someone they perceive to be in a position of authority does it first. I usually refer to it as the RLM effect, after how public opinion of the prequels rapidly shifted post-plinkett review.
The thing about old roundface here is that he to this day pretends to have been some pioneer in SAO bashing video essays, when in reality he was a late bandwagoner who jumped on over a year after the trend got really big, and long after it had been overdone and every possible angle of discussion had been exhausted. He has never offered up a remotely original thought, just cashed in on an existing trend and shat out a couple of videos in a day or two.
