Interesting concept, I like it. I'm not into fps in general, but here are my thoughts.
I felt a bit lost at first. The art style is cool, but some elements are blending together. I found confusing the fact that for basic enemies you have to shoot at their body, while for any others you have to shoot at their gem. Also aiming is a bit difficult.
Anyway, after some death I began to enjoy the game. The gunplay feels good and the game itself is pretty fun.
Because enemies are all around I would like to have some sort of radar in the UI, to give an idea of what's behind me.
In my opinion the upgrade screen shouldn't open and close by itself so fast. It's a bit annoiyng when I try to aim and suddently all stops without warning. Same goes when the game resume, I died once because the enemy was too close and I wasn't ready. You can either make the player open the upgrade screen by himself, or make a soft transition maybe with a countdown of some sort.
I'm not sure if the game can be called a "survivor-like". It's looks more similar to game like Returnal or other fps-rpg to me. But as I said, fps are not my genre, so I can't really say.
Overall you made a nice demo, was fun to play ^-^