There's IP I don't care for that still make darned good lands and attractions. Pandora is one and Star Wars (shocking but true!) is another. And there's IP that I love where the attractions could be way better than they are like Little Mermaid, Beauty and the Beast. Then there's the IPs that make me go, "Hmm, ok" but I love what Disney did with them- ie Cars Land and Legend of the Lion King.I agree, generally, but will point out that from inception, Tokyo Disney Sea has included a Little Mermaid land immediately adjacent to Verne Land. TDS really pioneered the use of single-IP lands and was generally well regarded for such.
I do. I generally think it falls into two categories, but both really just fall on the side of personal opinion. One idea being that people like to have a wide diversity of attractions and that locking lands into a single IP reduces the possibility of such. The caveat to that though, is that you have to make area lands and parks in general have these really broad themes that don't really mean much. At the end of the day, if TDS's theme is "the sea" you can basically make anything fit into it and *kinda* make sense. That's more of a six of one, half dozen of the other discussion though.
And of course the other one is simply that people don't care for the IP being presented, and really don't care if a land or park is based on a single IP, as long as it's one they like.
As a weird side note to this. I see that a contender for the most snooze inducing Disney movie that isn't Song of the South, and the reason why Discovery Bay got sunk, just made it's way to Disney+
Definitely curious what Imagineering came up with for the new Springs addition to TDS. Peter Pan and Tangled are two of my all time favorites.