Parts of it could (and probably should) have been cut. The bad anime fantasy sequence in the middle, and the "I Can't Fight This Feeling" song number at the end, were both embarrassingly seat-squirmingly wrong, and should be excised and those plot points made differently.
People looking for contemporary religious themes will find them, esp with the Mayor being ridiculed for his belief in a giant invisible elephant in the sky and how their safe and stable world was hovering on the edge of doom, and with Horton being ridiculed for believing in the existence of beings who could not be seen, touched, or heard. But that breaks down, in that Horton is not exactly an omnipotent god, but more like a vast lovecraftian being, and the Who's are hardly matterless spirits.
Come to think of it, the universe of this story is pretty explicitly Lovecraftian. There is no apparently kindly God, just a mind bendingly vast universe, full of beings of such different scales and powers, that one's best chance for survival is to luck into being someplace where you don't get accidentally stepped on, and an entire world can be obliterated without warning or fairness, based on the gust of a breeze somewhere else.
I liked it. Kids will like it, for the same reason that adults and kids have liked the source book for decades.
