Just because there are a ton of levels doesn't mean it's going to be samey and boring. This game is going to be lovingly and deliberately crafted, not randomly generated like a Diablo clone.
For an example of how different environments can be, check out the Underdark in Baldur's Gate II. One minute you're in a dark cavern, the next in an Illithid lair, then next at the bottom of the ocean. Have some faith OP. Srsly.