I rather like that the good guys can make mistakes and problems for others. I don't like the idea that main characters should have to always do the "correct" thing in the end. It just sounds too safe and boring. Regular Show has been going that direction, and it's not really as enjoyable anymore. And it's not even that bad in this episode, where the Gems aren't shown to be inconsiderate jerks, but more oblivious that they're causing problems.
As for the world-building, I'd say even a few eps of the first season of Adventure Time provided plenty of quirky fantasy elements that opened doors for more stories, and just made for a more interesting show. That and... well, it had adventure. SU pretty much stays in Beach City. I'd really like it to stretch out and explore more, because the Gems are worth learning more about.