First the good: Overall a solid foundation, the theme is there, the core game play needs polish with the AI and all, but its fun with the weapon pickups, the heart rip-out (that really should be the focus!) and the door slamming! (love that sound). I think you already know a lot that can be improved already game-play wise, just look at the roots of the game idea.
Whoever, there are a few things I found difficult while playing, like only now after I played it did I get that there was a combo system, and that's my main grudge: It has several parts that very unclear (visually),
The worst offender was the player bullets, but everything kind of just meshes into a big blur, especially with the light effects, the shifting colors and the camera shake. I get the idea visually, with the gore and all, but the focus must be on giving me information before all the cool effects (but also, the rest of the effects takes away a lot from the gore, the blood did not leave a impression on me). It all leaves me confused, I honestly felt like a lost track of the character at times (even if hes right in the center).
It really needs better contrasts between things and if possible a bit more screen to se more stuff (it was way to zoomed in for me).
Also, the UI information is also unclear. It might be front and center, but with all that's going on I dont have time to look at it, and frankly it felt like the UI was more in the way at the end, as I had to go downwards the UI hid the enemies. Its a nice doom throwback, but I dont know if it has a place in this type of game.
There where also a few mechanical things. I did not get the slide-skill, it did nothing for me, and this might just be me being bad at it, but I felt that It game me no strategical advantage. With the speed of the bullets it was not that useful.
I also had a feeling that there was a lack of speed in this game. This I cant really set my finger on, as the character moves fast and all, but it just lacked the "flow" I remembered from example: Hotline Maimi or Doom. Might have had to do with that all enemies where like turrets, and removed a lot of organic feel from the danger.
Keep on the great work! Looking forward to v.6 and onward.