Oh man, I don't even know where to start on this topic, so I'm gonna try to be as brief as possible.
I think the worst thing about the gaming community is the toxic people that thrive in games. People who feel the need to tear others down instead of lift them up, the sexism that I constantly see in almost all big gaming communities, and all of the "older & mature" gamers who feel like they're the only ones entitled to the game (example: "Oh no, it's a squeaker, I hate when kids play these games..."). Most of the gaming community is toxic. I especially hate how people treat others on teamwork based games. Many gamers tend to act self-centered instead of helping each other out.
Another thing that really bothers me is the whole "pay to win" thing. I don't think there can be much said about that. It annoys me that spoiled brats who spend their parents money win games instead of gamers who have worked and played hard.
The whole "graphics over gameplay" thing that everyone seems to jump on. Recently with Fallout 4 people continued to complain about the graphics, "Oh no, these graphics aren't super realistic, it must not be a good game,". It sucks to know that people avoid games because their graphics aren't considered to be the most realistic thing they've ever seen. But, then again that keeps the CoD kiddies away from good games.
There's so much more to elaborate on, but I'm gonna stop myself here.