Personally, I like detailed lands. The reason: most lands that aren't rigorously themed are messy and suffer from identity crises; specifically, the entirety of Hollywood Studios, Tomorrowland, Fantasyland, and Adventureland. (Future World has identity issues now, but it used to be pretty defined.) These all have random elements coming from everywhere as a result of minimal definition.
Contrary to popular belief, we actually do/did see strong themed lands in the Magic Kingdom. Frontierland/Liberty Square are pretty cleverly designed to flow geographically and chronologically. While the Haunted Mansion isn't woven into the lands as a story element, the area is structured and generally isn't jarring (though Splash Mountain is technically out of place). Meanwhile, Adventureland has no cohesion. Within eyeshot, you can see elements of the tropical islands, the Middle East, and jungles.
The most concerning thing to me isn't the lack of new rides; it's the lack of immersive rides. In 15 years, the only immersive and intricately themed ride added to WDW is Expedition Everest. As for Mission: Space, Soarin', Toy Story Mania, The Little Mermaid, all of these are decent rides, but I don't feel like I'm in a different place while I'm on them. I'm playing a video game, watching a screen, or on a borderline D-Ticket where I can see things hanging from the ceiling. What Disney needs to do is to continue building elaborate lands such as Anandapur, but fill them with elaborate rides such as Expedition Everest or the Haunted Mansion. No more costly exteriors with minimally immersive interiors (Little Mermaid).
Side note on Avatar: the franchise's staying power is irrelevant. Pandora can be worked into Animal Kingdom as a new, more cohesive take on something like Beastly Kingdom. It is a truly beautiful setting in the movie, and if they play their cards right, Pandora will be immortalized by its theme park execution. While I prefer new IPs, I see Pandora as (potentially) Animal Kingdom's much more expensive version of Splash Mountain. It's based on a franchise of questionable popularity, but can make for a heck of a theme park attraction, and that's what matters.