I think the problem with single IP lands is that there aren't that many IPs that are really conducive to one, especially from a business perspective. It needs to be popular enough for the IP itself to be a draw, but it also needs to have an interesting/unique setting that makes a whole land work. Plus, there needs to be enough in the IP to ideally support multiple attractions, shops, and restaurants.
Harry Potter works there, and Star Wars kind of works (it's a bit weaker on the setting part, especially as built, but the props help a lot). Pandora is a bit iffy on the popularity part -- obviously the movies have been incredibly successful, but it doesn't seem to have that much cultural penetration beyond the movies themselves -- but the setting works on its own even without any interest or knowledge of the IP.
Avengers Campus fails on the setting part, and I don't know that an interesting way to build that land even exists. Seems like it would always feel kind of generic.