Yeah, you actually finished a game, so that's a start.
Honest criticism though...IMO this just isn't a very appealing game. It looks like "C2 Ghost Shooter Tutorial: The Video Game".
-The bird's eye view is just..bad..pretty much no one does that anymore. All you see is heads, flailing arms, and the tops of walls.
-The graphics are "retro" but not in a good way.
-Literally half of the trailer is bland text saying "One _____" which...made me want to read the info on the steam page instead.
-Gameplay looks incredibly shallow. Games like these need to be complex. Lots of weapons, enemies, things to interact with, puzzles, suspense, dread, intrigue, etc. All I'm seeing is one guy in one area with one weapon fighting one enemy...over, and over, and over. Very slowly at that. There's just no substance.
-Apparently it has serious performance issues.
So, eh. My advice: Study and play other games like what you want to create first. Figure out WHY people enjoy them and what they liked and didn't like (same for yourself, of course). Use that as a base to meld with your own ideas and innovations. Most importantly: Get feedback early on. You don't want to spend a year or more developing something you have no idea if people will even like...again.