I'll never forget the guy who was basically hating on Melee for being hard. Was hyped for Smash 4 because he "could play competitively without having to spend hours every day practicing dumb advanced techniques."
I think there are a decent number of people on GAF who just really "mainstream" and casual gamers and don't understand much beyond that. It came up briefly in a previous Melee topic, but speedrunning also has a similar stigma.
I get the impression that they're not really "mainstream," but that they're more concerned with experiencing gaming as a hobby in terms of breadth rather than depth. There are so many games out there that it's hard to spend a lot of time playing one game and getting really into it if you want to play a lot of different games (especially when you're an adult with limited time which seems to define a lot of GAF).