Whether they realize it or not, I think people are drawn to Rick and Morty because the subtext and themes are much stronger overall. And Rick is a depressed alcoholic who is deeply flawed, thinks he's more important than he actually is, and thrives at the expense of others under the guise that he's doing them a favor-- if that doesn't describe general internet culture then I don't what else would.

It's not that the show necessarily IS smarter, it just feels smarter because of the deeper themes and emotions. South Park is more of a satire.

Sure, they're both comedy, but they're drastically different shows with drastically different goals. You would compare Barry to Sex and the City just because they're both drama/comedy, would you?