Thank you for taking the time to write such an in depth review especially as to why you liked our game and well things that maybe didn't hit the mark, from all of us we really appreciate it!
In terms of melee, it's mostly a numbers thing, some have more knock back but are slower and others are faster and some just deal more damage. It was meant to be a deeper system but we cut a lot of the complex mechanics out due to overscoping and wanting to focus more on the guns. In this case it leads to finding and using the guns as a very fun experience but with finding and using melee, it's less enticing.
Unfortunately for the repetitive gameplay it came down to once again overscoping for the amount of time we actually had. We had more ideas but we just cut so many to produce a final product. There were also supposed to be doors between rooms so that the player would have to fight all enemies in each room but we were in the final phase and we were still tweaking values for weapons and enemies.
Overall though the fact you had fun means that although the ideas that we had to cut probably could have made the game better, the base concept we chose to work with and refine really came to shine. All of us are very appreciative to hear your words!