Y'know, at the risk of contradicting myself, I got to thinking about things, and I guess, in some small way, despite the writing, Steve could be partly at fault for Kermit's personality and performance, if only because I remembered an example that I'm sure
@fuzzygobo and
@JimAndFrank would understand:
So, when Gary Burghoff chose to leave M*A*S*H, he wanted to be finished with the series altogether and expected to have his character Radar properly written off the show at the end of his final season, when the network decided to persuade him to return at the beginning of the following season to lead up to a to a big send-off for sweeps. When he came back, he apparently was really irritable, and it apparently showed through his performance enough that episode writer Ken Levine has complained about it on his blog years ago.
So, I guess yeah, maybe it's partly the fault of the writers and partly the fault of Steve.