I think the main issue right now is what Drtooth said earlier; the format barely allows for anything else in the show. There's too much emphasis on the celebrity/spoof segments and not enough time for regular Muppet material (of the 13 episodes in the new season thus far, only 5 have used the pre-Elmo-random-insert section to use a non-spoof/celebrity bit). I mean, instead of running "The Voice" a second time for no reason, how about something still recent that hasn't been re-run in awhile (like the Waiter Grover/Rhyming Day bit). The only character other than Abby, Murray or Elmo that seems to get plenty of material is Grover, who's been in 12 of the 13 episodes aired thus far from seasosn 43.
I understand the need to have more parental-hooking material, but parents can also be entertained by funny sketches, which they plenty of non-pop-cultural (like the Coffee Plant one; it's a Starbucks spoof, sure, but the focus is on Grover and Mr. Johnson and not the spoof element).
Really, the only complaint here is that there's no new E&B sketches. Sure, recasting Grover and Cookie did wonders for their usage, but they have plenty of material that they haven't aired yet; believe me, some of it's good and hopefully will appear on the show this season (the Monstruos Supersanos stuff is in widescreen, so there's no problem there).