Rick & Morty is for a more political / mature audience(and I don't mean mature as in age as they're all adult comedies I'm aware). South Park is just for anyone who laughs at fart / shit / vomit / swearing jokes or any other kind of sheer crudity. With all due respect it's a s crude as its low budget frame rate / animation. Rick & Morty instead takes the world's current events and satirises them in their own way, using intelligent jokes that you yourself have to be able to understand by being in the know, which is why some find it unfunny as they aren't in the know and don't appreciate the jokes. Rick & Morty may have the odd corporate worship like the Szechuan sauce but where Family guy differs is that it actually takes the piss out of how stupid those jokes are, kind of in a style similar to Monty Python.thats why they're usually done through Rick. It's a similar affair when they satirise race / sex / Jewish / other more controversial jokes, they aren't actually being offensive but rather they hit back at the kinds of people who make those stereotypes.
The cutaway gags are a popular part of the franchise's history , so it only makes sense that they keep them. I also wouldn't really see how Rick & Morty is actually lazy writing as they have more script writers working for them than any other adult comedy, maybe second to the simpsons but I'm unsure. But anyways,Rsck & Morty have actually done things that other comedies have never done - they wrote stories that have meaning to them. It's more than just s few jokes and goodnight, they've written many stories that have been praised for their handling and execution, for example, that one episode titled 'Pickle Rick', which dealt with the ethics of converting into a pickle to skip family issues and the tough decisions the fans have to go through for memes. So you not only get laughs, you learn a little something in each episode.