Not half bad, though it's a bit janky and I do have some core issues. Overall I think it was pretty cool (and the fact you've made a fully functional DOOM-style FPS from the ground up is remarkable, though I suspect that with some of the built-in features it actually internally might more resemble the more advanced Build Engine(Duke3D) or even Quake in some regards), but I want to detail all my criticisms to help give the opportunity to refine this into the best version of itself.
I've been playing DOOM for a long time and there's a few features of the engine I take for granted that I seriously miss. Namely... saving/loading and automap. If I could ask for anything it would be those. I've grown used to using the automap as an aid in navigation and especially finding secrets in unfamiliar WADs, and being forced to pistol-restart a level after dying is something I'm not a fan of as just about every DOOM source port will automatically reload your most recently made save when you die (and IIRC, they also autosave by default). I can understand how automap might be trickier to code in because it looks like you're using full 3D for level geometry, instead of DOOM's sector-based level format that made the automap easy to auto-generate.
Other things are that I've noticed (bugs and things I'd have implemented if it were me, but are certainly not hills I'm ready to die on): Backpacks stack -- getting both the backpack in the last and second-to-last levels will make your ammo capacity 4x normal. Also, while the fully animated status bar face is pretty cool, I can't help but think it should update as she takes damage as well (maybe making her look like a sad doggo when she's low on health). I've also noticed the aim assist seems to be weaker than in DOOM, not that it really bothers me so much to need better manual aim. Though it probably makes controller play that much harder.
Moreover, the keybinding system could use a little work, since not all controls can be rebound. And you can't rebind the "up arrow to shoot" key, so me being the weird guy that likes to use arrows to move in my DOOM instead of WASD... means I can't use my preferred control scheme without constantly wasting ammo... and the fact you can't rebind controls while paused ingame is a bit of a weakness here.
I also have a bit of a problem with how enemy AI, if a door closes between you and them, will always instantly chuck a projectile at you the moment they see you after a door opens. Those can be hard if not impossible to dodge especially if they're close to the door when opening it. Double especially given you usually can't open doors at an angle that will let you take cover off to the side IIRC.
Also off topic, but the music for the final level kinda gives me Painkiller vibes, lol.