People complaining about pixel-sprite graphics.
Similarly, people claiming any game that doesn't have a realistic look is for kindergartners.
Microtransactions and/or overpriced DLC.
When you ask for advice on a game and the only response is "Get gud."
Similarly, people who lob insults at someone for being a "n00b."
The rapid increase in internet/social media slang. If you don't spend most of your day on social media to catch these words as they're created you won't understand what anyone is saying.
People who think graphic violence in a video game is fine, but nudity is crossing a line.
YouTube's copyright infringement policies (I guess "fair use" doesn't exist anymore).