I tried sooooooo hard to like all three of those films but I just couldn't. MFS was probably no 1 that just had no Muppet appeal at least IMO at all. As for the other two films ehh...I just don't like when their roleplaying. They really lacked greatly of what Jim Henson did.
Ttch! No wonder why you thought you outgrew them.
You needn't have me bore you with the same opinions I've always said about those three movies... MCC was missing quite a bit, MTI got some of it back, MFS lost something else in the process. The only preferable thing about MFS over the others is that it had the Muppet characters as themselves.
MCC and MTI you can at least blame the direction they were confusedly going in, trying to ease a recast Kermit into the world by giving him very small parts in his own movies. Something that wasn't remedied until VMX and KSY when he was back to the starring role where he should be. And we all know the MFS mess by now.
The new movie managed to get as much back as we remember about the characters as possible. Hopefully next go around that tiny little extra spark will be added and everything will be 100% back on track.