Okay so having played it - (I played the Mega Drive version) - I feel what you need to focus on is making gameplay more skill based. Your movement does not really allow you to dodge enemy fire, and unlike in original you cannot use skillfull aim to take down enemies quickly. So the game becomes a little bit uncontrollable. Crouching doesn't do anything and appears to be only used to switch weapons because all weapons are perfectly auto-aiming - that's probably fine for player, but I'd remove that for the enemies, and constrain their aiming abilities to few specific angles.
It is incredibly impressive, so these two cents are just meant as a constructive feedback, not as a takedown.