I don't see why it would have to be "varied". In fact, there's a decent argument that "varied" is a problem with an IP land since you have limited space and can only provided a certain specific environment (or a limited few). This is an ongoing argument with the "difficulty" with doing Star Wars in a park due to the variety of places visited; which is why they opted for someplace entirely novel instead.
That's also why Cars Land works so well because the plot is so driven by the town which could be reproduced. It's not like anyone cares that the various race tracks or any (non-Radiator Springs) scenes from Cars 2 aren't included.
And I'd also dispute your last point, but, as you note, people can disagree. The whole selling point of the movie and why it was so incredible popular was because people wanted to see and experience the landscapes of the setting. Bringing that to life in a real place you can walk around is something that I believe would be a draw for a number of people as it is the memorable feature of the film. Heck, the Zhangjiajie National Forest has had
a significant uptick in tourism since the move came out.
Actually, I think this is actually to the detriment of an IP land. It really limits the storytelling and potential experience to just be doing book report stuff or having clear tie ins to established characters/scenes/events. I think this, for example, is why Gringotts is IMHO a much weaker attraction than Forbidden Journey. The latter has a loose narrative that lets you experience aspects of the IP, the former intentionally puts you within a specific known story.
In a sense, being free from being tied to the plot line of
Avatar while being able to use the fantastic setting is near ideal for a theme park use of IP. Historically, great theme park lands often revolved on developing experiences that enhance and relate to the setting and environment without having to be a slave to a specific story.
This one I'll give you, though personally I don't care as much about the stuff they are trying to sell me. I just hope that whatever they do have is interesting (merch) or tastes good (food). I will suggest that Butterbeer isn't
just popular because it is featured in the books/movies, but because it actually tastes pretty damn great. It's not like everyone raves about Pumpkin Juice.