The point of the carousel is that it’s fine... “if you don’t wants to go anywhere,” but Mary being Mary converts it into a fantastic adventure. WDW seems to be looking at this and saying “let’s take out the fantasy... and the adventure.” There is nothing particularly special about the Poppins carousel in and of itself.
To the people arguing that Disney parks needs A and B tickets... why? As fans, our goal should be nothing but Es. There is little Disney Magic that can imbued into a flat ride that can’t also be found at Six Flags, whereas even the most basic dark ride like Toad achieves a level of artistry found in very, very few other parks. No one goes to the Louvre and says “well, this is all fine, but we need some black velvet portraits of Elvis for variety.” There is not one dark ride at a Disney park I’d want to see gone and not one flat whose removal would bother me.
As to other common pro-flat arguments, flats, as far as I know, aren’t particularly helpful in terms of capacity - a ride like Monsters Inc eats more people than Arthur’s Carousel, and omnimovers dwarf a flats hourly capacity. The only real argument is an economic one, and its one we shouldn’t accept. Disney has the money, and even with the current construction projects they aren’t close to making up for well over a decade of neglect.
Look, EPCOT has no vision, and given the modern corporate environment, it is almost impossible it will ever have a real one again - that would require Disney to say something about the way the world is and should be, which is dangerously close to expressing an ideaology, something it will never do explicitly. Putting dark rides based on country-specific IPs in World Showcase at least offers an avenue for growth, one preferable to things like GotG in FW. A few days ago I was thinking that with Rat, a Mary Poppins dark ride, and one more dark ride in another country, I’d really be excited to visit EPCOT again. Of course, I had forgotten this was WDW in the 21st century.