It means it's become popular with "normal" people.
Basically, anyone who calls it that is no different than hipsters who'd get pissy when some obscure band they like got discovered by the masses. Because they don't like things simply because they like them, they have to use it as part of their identity. And when the unwashed peasants get their grubby hands on something, it's forever sullied.
Or to think of it another way, it's just petty in-group/out-group gatekeeping. Like when memes get used 'IRL'. The memes are just as retarded when they're regurgitated here, but when "The Other" appropriates them then suddenly it's bad?