I understand the historical significance of it, but a theme park attraction should justify its own existence beyond historical value. I don't ride the Matterhorn because it's the first tubular steel coaster, I ride it because it is fun and well executed. I don't think Snow White's Enchanted Dream should be preserved as-is for all time since it was one of Kim Irvine's final projects before retiring. I loved TTBAB, but I wouldn't say it deserved to stay because it's the last project Kevin Spacey did with Disney parks.
Apples and oranges, I know. But Muppet Vision was dated. It was no longer pulling crowds nor drawing the same appreciation the attraction deserves. As people have shared here, many modern folks would see the show and shrug it off as a one and done.
If Disney is going to replace it with a show that draws better and garners more appreciation from guests, then I'm for that. It stinks that it will vanish from the earth, but that's a world I'm used to with live theatre. These magnificent pieces of art exist until they aren't pulling in the audiences required to offset the work/cost, then they vanish into the ether. 30+ years is a great run for a 3D film.