It has been called all sorts of things and does indeed seem to have been poorly-received, which is a pity as it did see quite a number of improvements over DD. I think a lot of the criticisms were highly subjective and the quality of the voice acting was probably the major one: clearly they learnt from that as the voices in Divinity 2 were way better than its predecessors, but other than the infamous Death Knight I'm not sure the overall VA wasn't that different to DD.
For me personally the main reason I didn't play was aesthetics: I like my fantasy game worlds to be verdant, pretty-looking places (yeah I know, even if they are filled with psychotic wildlife that wants to kill me at every turn) and for the most part BD just looked a bit too uninviting and alien: to jaggedy and to grey-and-black for my taste. Even Morrowind which wasn't as severe just being the sea of greige that it was I heavily modded to have it covered in grass, trees and flowers.
I know I'm kinda the one missing out but it did bother me enough that I only played about halfway through it. I guess I view games as a major part of escapism for me, especially being the agoraphobic sort, and I didn't really want to escape to a dungeon dimension!