I'm nostalgic about the Muppets -- I grew up in the 1970s-80s -- but also as a kid, I was aware of IPs (though the term probably didn't exist then) like Betty Boop and Popeye and all the stuff in Toon Lagoon. And while I watched that stuff (heck, we only had three channels so there wasn't a lot of choice), it felt dated and from another era.
Even Looney Toons, which I enjoyed, felt dated in the '70s, with all the references to crooner-singers and old mobsters and the Brooklyn Dodgers (I lived in LA)...things from decades earlier.
All that's to say, sometimes these IPs just reflect an era and while they can be appreciated, deeply, nostalgically, they may not be relatable or relevant to kids. That's not a terrible thing, we have to make room for new ideas, new creations.
I agree Muppets+inverting coaster is not the perfect match (a kid's coaster like Chip 'n' Dale's or Barnstormer may have been perfect for the sensibility, and if made twice as long and include a couple of animatronic scenes, may have been great.)
A bit of an aside, but sometimes Disney does things which feel "close" but not perfect. You can almost feel the behind-the-scenes debate that must have gotten them to their slightly compromised decision. It would be fascinating to be a fly on the wall and hear the discussion and trade-offs. We're here in a forum exchanging opinions and feel some level of passion with no stakes at all, imagine going to work each day and having to do that with colleagues or bosses that you have to maintain a good relationship with long-term.
And also knowing every decision will be debated again by the public later!