Yeah, given the sum total of work produced by Henson as compared to that of whoever it is who does the Wizard of Id, I believe we can't really put the blame on Jim.
I meant Jim Henson couldn't be bothered to write more Wizard of Id jokes, but he deserves some kind of posthumous award for being able to write any. BTW, Wizard of Id was co-created by late creationist wackaloon Johnny Hart.