Agreed (although not in that hyperbole). Variety is no replacement for out-right design quality. As long as the environments are engaging to navigate and look at. I don't really care.
I mean, arguably Demon's souls didn't have much "variety". They were all some variation of stone structures, sans a boggy swamp. it was the little things. Like the sound design. the lighting. the clever locations that really sold it.
I agree with what you're saying in regards to Bloodborne. In Demon's Souls' defence though, I think each "stage" is fairly identifiable to the player, each possessing a different and unique vibe/design.