Here are a couple more minor pieces of feedback. I think adding hit stop, camera shake, more pronounced particle effects and sound effects could go a long way to make combat feel more visceral. I'm assuming you are making this in Unity? (Sorry if this is too much info or you already know all this stuff, just trying to help)
In unity for hit stop effect, make a coroutine like so:
And you can call this with StartCoroutine(hitStop(x, y));
I would call this whenever a player bullet hits any object or enemy, I would make x = 0f, and y = 0.05f. Similarly, I would call this whenever the player gets hit by anything, with x = 0.2f and y = 0.2f.
Whenever an enemy dies, I would call it for longer: x = 0f, y = 0.3f to really emphasize it.