As to why they seem to think a land consists of 2 attractions, it comes down to how things get approved these days vs. how it happened in the past.
In the past, there were overarching tenets regarding what would be successful in the long run, and obviously most of them originated with Walt. One of these was the belief that the big attractions, your D and E tickets, got people in the door. The A, B and C tickets might not actually cause somebody to make a trip, but they made the experience much more enjoyable. Rather than just going from long line to long line, there were nice, high quality smaller attractions to let people flesh out their day.
Flash forward and the problem becomes these tenets, by and large, no longer exist within Disney. So if you want to build an attraction, you need to tie that attraction directly back to a revenue stream. Whether it's more people through the gate, increased plush sales, or whatever, you need to make that case to executives that really have no understanding of what its like to be an average guest in a Disney park.
So if you pitch them a D and an E ticket with well-known IP, you've got a chance. But ask for some more cash for a couple of A's and B's to go along with it? Good luck. From their pov, why spend extra millions on something that, in their mind, is not going to sell any more tickets. And if you do manage to get a something "extra" included, there's a good chance it will be cut and never see the light of day.