I think one of the "problems" that AK may have is it truly is full of unrealized potential. Disney just has not pushed the boundaries of what this park can be. So much has been left on the table in terms of what could've been done. The world of prehistoric animals has barely been realized, underrepresented areas/animal life from around our current world, and outside of the Yeti, nothing to speak of in the mythology/fantasy front. The attraction line up should be spectacular. Personally, I'd love to see AK as the natural worlds EPCOT. Unique attractions, focus on the science of the animal kingdom, using relevant issues (conservation, endangered species, etc.) to help tell an intriguing narrative with amazing and imaginative attractions. And an amazing menagerie of mythological creatures.
But, to be absolutely clear, I LOVE the Animal Kingdom. I just think I see why others may not so much, at least some of the reasons.