Hey don't knock Kevin Clash for being to busy with Sesame, he is doing a wonderful job over there, and is really what the show needs. I know a lot of people do a lot of Elmo bashing and it trinkles down to Kevin as well. Read his book and you will learn and grow to not only love Elmo, but also appreate him.
There is no way you can compare The first season of the Muppet Show and the first Season of Muppets Tonight. they where to very different shows, with some of the same elements.
There was a lot of what do we do know after Jim passed, and I think that Muppets Tonight was one of thouse things. The writers (who one of I'm friends with) Where not trying to bring back the Muppet Show and all it's glory. They where trying and doing a good job of intorducing some new Muppets along side the classic Muppets. The same as with the Jim Henson hour, and I think that is what hurt both shows. There should have been more classic Muppets and slowly bring in the newer ones.
As far as Cliford not being well rounded by the time Muppets Tonight was filiming and airing Elmo was gaining a whole lot of popularity, and if the show had keep going they would have had to change things anyways beacuse Kevin was going to have to do more at Sesame.