Because the Muppets does not fit the attraction, other than having a band. Their image, character, and dynamics does not fit what Rockin' Rollercoaster was.
You took a cool rollercoaster, with an intense 2.8 second launch, Rock Music, theming that teenagers and adults were attracted to, and turned it into a classless, juvenile, immature, and childish look with unlikable characters.
This is the same as changing Pirates of the Caribbean to Pirates and the Cabbage Patch Kids.
I find it interesting how accepted this is. Considering this is the same forum that has been complaining about a motionless animatronic for years, crying about the loss of Dreamfinder and the original Journey into Imagination, how Frozen doesn't fit EPCOT, losing Splash Mountain, to name a few, but any distain to this change is "wrong"?
Everybody I discuss this with in person is disgusted. Do people argue just to argue, or is this something you are genuinely excited about?