Thanks for playing!
All walls are breakable but explosive damage does a lot more damage to them than other sources, so regular bullets for example will take a lot longer to break them. I've tried to keep enemies and their projectiles the most visible things, but yeah it can be improved. It isn't really meant to be a survivors type of game (closest equivalent would be something like Nuclear Throne) so the way the game is designed I don't think automatically firing your guns would work.
Not looking for anything specific, just anything you can think of really. More thoughts are better than less.