Hardcore gamer = someone who plays only cinematic grizzed white dude games and/or military fetishizing FPS
Casual gamer = anyone that is not a 15-25 yo male, and/or plays anything outside of the previously mentioned games, especially if those games are colorful.
So basically the gaming community is full of gatekeeping, misogyny, toxic masculinity and general chuddery. They make sure they're the loudest voice heard when anything about games is talked about, and won't be happy until all games a homogenous stream of bland, hyper-realistic but with a grey filter slog of mindless action with no heart or soul. And don't you dare force them to read any dialogue or story.
The way you phrased your comment makes it sound like your take is controversial. Are there really a lot of people who think otherwise?
I had never heard of them until Milo Yannopolous got popular in 2016. Back then, it meant "alternative right" as an opposition to GOP establishment and RINOs. Boy, they sure got a lesson in entryism as every piece of shit in America jumped on the train.