I've heard the "adult" turned out not to be so much dirty, rather more mature themes, like emotionally.
I guess that's fine. I like the Muppets well enough, they were a big part of my childhood and I enjoyed the two recent movies quite a lot, but I've never been one of those people that didn't feel like they had enough Muppets in their lives. I don't so much dislike the idea as not need it.