I will say based on my recent visit, there are definitely places that, while successful as a theme park, DAK "fails" as a zoo, such as:
- Limited viewing opportunities. This is the most common complaint I've heard on this site, and in my opinion a very justified one. The animals on the Safari cannot be viewed for longer than the 30 seconds to a minute the truck is there, while many zoo enthusiasts may want to look at certain species for longer.
- One of the main goals of the AZA is education. From what I saw, DAK fails to reach this goal. Signage is missing at a lot of exhibits, and some of the staff members stationed at exhibits weren't exactly helpful (one of the staff in the Asian aviary introduced the Crested Wood Partidges as "avocados with legs")
These two reasons mean that zoo enthusiasts are justified in being critical of Disney's Animal Kingdom, as it succeeds as a theme park, but simultaneously "fails" as a zoo.