What went wrong with the 2003 version? That couldn't possibly have been that bad, considering the alleged movie version of The Cat in the Hat came out the same year.
If you mean the '03 Peter Pan, no, it wasn't Cat in the Hat bad, more like Tim Burton's Alice or Narnia-sequel bad--Where they take a seemingly screenwriter-proof classic, get full of their own big budget, decide to "cure" the classic for a popcorn audience with the usual screenwriter embellishments of big action scenes and easy laffs, and start embarrassingly futzing with the original to points where the author would turn over in his grave.
(Wendy did NOT have an "Aunt Millicent" to say un-PC Victorian things and make her feel burgeoning feminism...Peter did NOT have a "romantic subplot" with Wendy, quite the reverse in fact...Saying the "I don't believe" words does NOT kill specific fairies on contact like Raid...Yes, Nana was a St. Bernard, but NOT Beethoven out of the John Hughes movies...And call it a minor nitpick, but in the final battle, Hook did NOT freakin' fly. And I know I'm forgetting at least half a dozen other cringe-worthy heresies, but I don't want to go back and look at it again just to make a list.)