The Depths is, realistically, nothing all that new. Zelda games have spent a lot of time exploring 2-world situations.
Light/Dark world in LTtP,
Young/Adult Link in OoT,
Twilight/Daylight in TP,
Hyrule/Lorule in LBW
Seasons or Ages in the Oracle games.
The Depths feels like the LEAST inspired of all of those, since the only way to make the worlds interact is to drop things through holes, which was only needed in one sidequest. I'd like to see a modern Zelda game where the two worlds can influence each other. For example, a rock is breakable only in World A, and after breaking it and going to World B, that rock is gone and was hiding an entrance to a cave.
