As Garooth and GA-MBIT pointed out, fans of Pokemon (hi!) tend to focus on the actual Pokémon, not any single location. Having the land be yet another region specific to the theme park that would fit alongside Kanto, Johto, et al. isn't a problem at all. In fact, the world of Pokémon is described pretty much like our planet but filled with Pokémon. What you perceive as a weakness because there isn't a unique place like Hogwarts or Bowser's Castle doesn't count against Pokémon the same way.
What people are most likely wanting to see—and definitely what parents are most familiar with—is Pikachu (maybe Charizard), and of course most of the starter Pokémon; visual marketing will not be a problem. There are so many we'll never see all of them but I hope over the years several are swapped out either in the ride and/or in the land over the years so we do see different ones. I've mentioned it before but this would also allow the AAs to be taken out for maintenance and not detract from the show quality because a different Pokémon can take its place.
In terms of physical places most towns in the games and anime have:
- Poké Mart (merchandise opportunies)
- Pokémon Center (think JP's dinosaur hatching kind of thing, rest area)
- Pokémon Gym (could be a show with different battles and Pokémon seasonally)
Even the buildings have a general feel but doesn't stick to a particular style meaning how it shows up in the park can have its own style. The Pokémon Center in the games for example (taken from Bulbapedia):
View attachment 24380
As long as we also have a Nurse Joy, an Officer Jenny, and a Pokémon Professor (meet-and-greet with different ones like we do with Transformers) along with at least one solid dark ride, a small coaster and/or a flat ride, it'll be great.
This is all to say that a land by itself which isn't really from any one game or episode/series isn't as important as the Pokémon we'd find there because (personally speaking) I'm only there for the Pokémon.
It might be that Universal and Nintendo are waiting to see how the Pokémon ride does in Japan both in guest satisfaction and popularity to gauge what gets built elsewhere. Do I think that IP deserves more than a single ride? For sure. But I've also seen how little effort Game Freak puts in their main games at times that leaves me scratching my head so who knows what we'll get.
If they do go ahead with a Pokémon land, I hope it's built from scratch and not retrofitted into Simpson's (or whatever land they use) existing infrastructure.