Because of the belief that the bible is quite literally the word God JWs must shut out many logical concepts and theories. It's not just evolution although that is a large one. I know when I was in there were certain concepts that made sense to me but I would try not to think about them too much. Here are a few:
-Morality as social construct
-Death as natural process
-The expansion and ultimate end of the universe
-The idea that life may exist on other planets (even if we may never be able to reach them)
-The concept that human intelligence could be transcended by an Artificial Life (singularity theory)
-The idea that multiple universes exist
Many of these ideas are fascinating and it's been refreshing to think about these things without thinking that something is wrong with exploring any idea to the full.