He has gotten kind of soft around the edges. I think there's one thing the Muppet writers have been forgetting in regards to Kermit: he has faults!. Here are some examples:
He loses his temper all too frequently, at Piggy, Fozzie, Gonzo, etc.
He can dish it out but can't take it. In the Ethel Merman episode, he makes a lot of short jokes about Fozzie's tiny agent, Irving Bizarre. When Irving makes a frog-warts joke, Kermit yells at him to get out.
Kermit has an ego, AND is presumptuous. Whenever a guest star talks about their "favorite Muppet" or "the most important Muppet", he AUTOMATICALLY assumes they're talking about him. The Teresa Brewer, Jean Stapleton, and Marty Feldman episodes are all examples. Other Muppets know about his ego as well- in the Sylvester Stallone episode, Scooter KNOWS that Kermit will let the groupies (Sly's groupies) stay in the theater if he thinks they're there to see HIM!
Also in the early days he was flirtatious- Juliet Prowse and Connie Stevens were both in a manner of speaking hit on by The Frog. Juliet was cajoled into kissing him, twice, and he said to Connie "At last we're alone."
Nowadays, he comes on too fault-less, more like Mickey Mouse than Kermit the Frog. The fact that Kermit isn't perfect is one of the great things about him, and it's an element that has been left in the dust for a while now.
David "Gorgon Heap" Ebersole