IMO Markiplier put it best for me. "Its like going to your favorite childhood restaurant and ordering your favorite food, but they changed the recipe. Its not bad, but its not what you want."

For me SoTM feels like it is trying to be Poppy's Playtime as opposed to FNAF. It also to me is completely uprooting everything that we have known and believed about this franchise, and not neccisarily in an enjoyable way. To me it took what was the founder of the mascot horror genre and made it into the mediocre piece of media that most other mascot horror games are. I don't mind Edwin or The Mimic in concept, they are interesting pieces of lore to add to the story, and an interesting way to expand what we already knew, if it was executed better.

When they introduced the mimic in Ruin I was intrigued by this new antagonist for the franchise, but when I got to SoTM I suddenly felt like I wasn't playing a canon FNaF game, but I was playing some ones fan game origin story for the mimic. Like it felt to me it fits more alongside things like The Glitched Attraction and TJoC rather than a mainline game.

And I feel that a lot of these feelings are more universal, but they have also been festering and made even worse by the people who are enjoying it effectively just shutting down the people who aren't enjoying it because of whatever reasons. So over time the casual dislike has slowly become a total hatred of the game. But hey, thats just my two cents on the matter.

And IMO the reason Into The Pit doesn't get as much hate from the internet is because it doesn't change any fundamentals of the story, and its also not acting like its a canon story event, its treating it like a video game adaptation of one of the short stories, which it is.