I think it's pretty normal that as people get deeper and more invested in any given artform, they tend to become more appreciative of works that are less immediately pleasing to lay-people. You mentioned literature and (atonal) music, but this just as readily applies to food, wine, videogames, Anime, fashion, anything you can think of.

I'll agree that there's an unfortunate tendency for some people (again, in any artistic field) to get overly critical or dismissive of straightforwardly good work, especially if consuming, thinking about, and discussing the quality of work is their actual job and they're perhaps getting a bit bored of something they once loved. On the other hand, who better to recognize oversaturation of a given style or approach? I certainly wouldn't notice that wine producers are currently chasing the trend of dry whites, produced from heirloom European grapes to the detriment of all other kinds of wine! It's important to have at least some snobs, to push and goad artists away from currently oversaturated trends and continue the cycle of innovation and variety. And it's important to recognize that a critic complaining that a certain style is too popular doesn't mean they think it's a bad style or that you shouldn't enjoy it, just that they'd like to spend more of their life enjoying other things too.