I liked 3D Land, but it's probably best not to presume that it's universally loved, as it clearly isn't. And even among those that do enjoy it, it's probably not best to assume that everyone is on board with that as the vision for console Mario platformers.
Yes. 3D Land is excellent, but the point is that Nintendo created a certain expectation that 3D World doesn't live up to. Like, the entire thing, and Wii U line up as a whole, comes off as creatively bankrupt. For its blunders with the Gamecube, at least Nintendo took some chances back then. To be fair, the 3DS is doing great and another story entirely.
And I'm sure 3D World will be great. My main concern with its quality is the multiplayer. When your game needs to accommodate four players, you end up with more space, larger platforms, etc. Motorcycle versus a minivan.