Agreed. While I too want to see Chekhov's Starship fired, I find the character stuff quite fun. And while "lighthearted fun" is, well, fun, it is just a little snack compared to the meatier drama that a darker series can provide.
The problem is SGU, like BSG did, accepted the credo that dark situations make for dark people. I'm all for serious and crap like that, but I didn't drink that particular Kool-Aid.
So that was the story Star Trek and B5 and even SG-1 wanted to tell. The fight against evil and injustice is a battle without an end, but if you fight it well, if you stand to your guns, sometimes it can be won for a little while.
BSG wanted to tell that story too, at first. It would have told it in a gritty way, no doubt, but this is not a bad thing. Sometime though, standing in the mud, it lost its way. And it never really found it again. Stargate Atlantis did something similar, though its swings were more abrupt and extreme.
SGU was never on the right path.