I replayed it and I'm updating my takes
The environment design wasn't the issue. I just hadn't realized the doors were more than props. Maybe add some non-locked doors so the player can understand that doors exist, or add an "E to Interact" prompt when getting close enough to do it.
While I still think the shotgun is a little overpowered, the Auto-cannon is okay
The lighting was caused by the bug, not by anything of your doing
I still ultimately think that the appearance of the game could be more unique, as right now it looks forgettable. I can barely remember any of the designs for ANYTHING. The only designs i can remember are the health-pickups being orange squares.