So obvious disclaimer, spoilers for the new season if you haven't seen it.
In this season the entire town is divided and fighting because of a single online troll who keeps everyone fighting by causing everyone to point fingers and stop trusting each other.
Meanwhile the election is going strong between a giant douche and a shithead sandwich, and anyone who starts to really questioning what is going on is distracted by "memberberries", these berries that are constantly reminding people of nostalgic pop culture references.
So I think they're really trying to get at some of the issues going on right now. I think the main theme is the whole Hegelian, divide and conquer premise where one lone, disconnected person can sit comfortably in their office and sip wine while dividing the community and watching them destroy themselves. As a side note this character happens to be Kyle's dad, the only Jews on the show. I've seen some people speculate this is a veiled reference to Israel. I have no idea.
The other theme is that any time people try to deal with the issues we are facing, they get distracted by the member berries, which likely represent pop culture. All you see on TV these days are remakes of old '80s series or movies and I think they're pointing out how that is being used to distract us. At times it seems as if the writers are double-tasking the memberberries- They may also represent our culture's current fascination with looking backwards instead of forward, and representing our dependence on (mostly legally-prescribed) drugs to escape reality and actual deep thought. When you get intellectually lazy and curl up deep inside your own narrow worldview, casual fascism comes easy... That sort of thing.
The last theme would be the U.S. prez election, but I'm not exactly sure what their point is here. The person representing Trump keeps trying to give up saying he's no good and Hillary would be better as president, but Hillary is such a robot she just keeps repeating that her opponent's statements are lies. Even though Trump is trying to throw the election people just like him more and more because he's being "real."
EDIT: People's comments in this thread have reminded me of one missed theme so I will add it here. Cartman was forced to abruptly quit social media and his phone was smashed. At first he was very unhappy. Then he meets another girl who has disconnected and she shows him the park. They hang out there and Cartman becomes very calm and eventually makes a connection with the girl, and she hints at them having a relationship. This is something Cartman could have never done in past seasons because of his trademark a-hole personality.
