The idea of instead of the audience growing out of the show, it might be the show growing out of the audience. I don't agree with a lot of the opinions completely I feel like south park is still in many plays doing their " playing both sides of the fence" thing, but the thing is last season, a lot of times, the one of side of the fence was just... way more a thing than the other side of the fence.
The idea behind of a lot of it was a lot of south parks humor, or rather more and more over time has become a " look at these crazy kids and their PC whatever" which in some cases is funny, but I understand the sentiment. The idea of the idea of some show just getting a bit too old for their audience is just an interesting idea. And its an odd thing to consider, because south park , kind of have always made fun of things kids were into. Chinpokemon the dance battle stuff, but its something about making fun of the concept of PC has just turned people off. Because on some level what are you making fun off? And even more so, the delivery is a heck of a lot different that before, the move to a more structured story over the course of a season, has in some ways made it worse. Before they would get their point across in one many two episodes, and be about it. But now with a whole season of getting the point across, not only could the point not get across. If they actually don't have a point, its a whole season of miss.
edit: To add on to that, I think the definitive proof of them just , in a social commentary sense having outgrown a lot of their audience, south park works best at least to me nowadays... when it isn't south park. My favorite episodes of south park are the mysteron episodes, because its about the kids wanting to be super heroes, my favorite peices of south park media is stick of truth because its an rpg. When you give them jokes in a general setting that don't really need to be culturally biting in today's world, but let them just nerd out. It works great, but when they try and be hip, while you get some funny episodes like tweek x creig ,sometimes it just falls apart. I am infinetly more hyped about the new south park super hero game than whatever possible next season.