I personally disagree on Skyward Sword. Or maybe the intentions were good but I feel that they spent so much time working on the controls that they neglected the rest of the game.
Skyward Sword has more dungeon content then any Zelda by far and much of that content is based around said motion controls. Just because the overworld wasn't as large as Xenoblade doesn't mean it wasn't ambitious since that was never the goal. They even said the goal of Skyward Sword was to make something that was one giant dungeon like experience, hence why all the overworld area's were like dungeons.
It's kind of easy for a game like Xenoblade the have a large world when the actual gameplay in it's world is no where close to as complex as the gameplay in Skyward Sword. There's no puzzles in the environments that you're interacting with, no maze like structures that require different items to start changing said environment. The world of Xenoblade only requires the designers to draw something and then call it a day. The world of Skyward Sword required actual thought into how the puzzles in one area, can effect what going on in other area's. Not to mention coming up with a lot of unique puzzles for each area that can take advantage of the new items the players keep receiving through out the game as well. Combined with the fact many of these puzzles are part of the actual environment, yeah, it requires a lot more work to design something like Skyword Sword's world.
This is why the 3D Zelda are still the most unique kind of games out there. Everything people love to compare 3D Zelda games to are nothing like 3D Zelda's since many lack even the most basic puzzles. This is why a lot of other 3D games have larger worlds because the designers don't bother with puzzles since those are a lot harder to make, which frees the teams up to make larger worlds.