I think the tutorial should flat out say that the game is audio based and there are no visuals other than the score and some star trek hyperdrive particle effects. Then, it should also mention that the positioning is sort of like Galaga, where the ship is always facing the same direction, and movement strafes the ship to the left or right. I originally thought movement also rotates the ship, but that is not the case. It took me a while to figure those things out or I had to ask or read the comments, so more description in the tutorial would be helpful.
It feels weird having to hold space to charge your laser, I'd say it should shoot right away when you press space and maybe has a cooldown instead.
Lowering the volume of your own ship's laser and especially movement would help. I had a little trouble hearing enemy ships over my own ship.
I got about 2000 points after I got the hang of the game. It seemed fair whenever I got hit. I'd usually get hit when I heard the enemy and I moved in front of them trying to shoot, but I got shot instead. So there is some incentive to go back and try again to do better.
I don't know! I just didn't find the gameplay all that fun. That's cool that you're going for a game that is accessible to vision impaired players, but I think it needs more. Or maybe I did not get far enough to see the ramp up in difficulty. My favorite game to play without looking at it is probably the old Pokémon RPG games, when you're just walking around in the grass looking for rare Pokémon, grinding up levels, or hatching eggs. So maybe adding a level up system or a way to unlock more ships or enhance your lasers could make it more fun.