Kermit may be one of the most straight faced of all the Muppets, but he is DEFINITELY not serious. He's always there making a pig joke, cracking a one-liner or just being his own funny self.
I don't understand WHY we're talking about how Guy Smiley would've made a better host than Kermit. I'm not going to add fuel to fire by agreeing or disagreeing, but the fact remains, The Muppet Show was thirty years ago, and guess what? Kermit was the host. He always has been and always will be. You can't change that by making other people believe it. Or should Disney edit all of the other Muppet show episodes and superimpose Guy Smiley of Kermit? (I'm sure they could do it while they're editing Eren Ozker's Janice voice...)