Segel writing himself into the film as Gary was just self-serving, pure and simple, in my opinion, and I think having a guy previously known for nothing other than Judd Apatow films may have hurt the film's marketability. On the other hand, I feel like no matter what the studios would've wanted a marketable A-list star to play a major role, and Amy Adams, a great and diverse actress, fills that niche nicely.
There was a lot of focus on the human characters, but no where near classic retelling levels. I don't mind the Gary/Mary subplot at all, but only because it's a subplot. It gives some sort of tension to the Gary/Walter subplot. I tried thinking of what would happen if Mary wasn't in the film, they probably could have done it without her, but then there wouldn't be tension to the human catalysts. The plot was mainly about saving the Muppets, bringing them back together, and I don't think it would have worked out the same if it was just Kermit slamming his fist down and saying, "I'm getting everyone back together."
We WERE going to have to have some celebrity being a large focus. That's what the Classic Retellings were. If we got one of those, we'd relaunch the franchise to classic retellings, each getting less interesting than the next. This was the film that had to be made, this was the story that was meant to be told, this is the film that will relaunch of franchise of endless possibilities.
If there's anything outside of the Muppet franchise I think this could be compared to, it's probably Looney Tunes Back in Action. That was supposed to relaunch the Looney Tunes, and it completely failed. The humans were much more the focus and much more 1 dimensional, said humans were completely worthless and useless to the movie, there were more throwaway gags than plot, and of course there were huge behind the scenes conflicts with studio meddling rewriting the movie to make it less comprehensible. We could have got something THAT messed up that would have sunk to the bottom of the Box Office as soon as it came out. And we ALL know what happened to the Looney Tunes after that movie failed.
Everyone's problem seems to be about the same thing...
editing. I don't know if the filmmakers even got the choice to make those cuts. A few more scenes would have made the difference, I agree. But what's there was enjoyable, most people loved it, and we're going to get more stuff out of it as a result. What's wrong with that?