Right now, this is a fairly average space shooter. If you want to polish the project properly, I have a few points:
- First, the targeting needs to be fixed (initially projectiles fly toward the intended targets, but later they start picking not even the closest ones, but seemingly random targets). Alternatively, you could add a reticle and let the player control aiming.
- Second, add a bit of engagement to the gameplay loop. This could be anything: backstory, lore mentions, or more explanation about the controls and the game's objective.
- Third, it would be nice to add music—something in the vein of classic space shooters.
- Fourth, and most importantly in my opinion, give your game a unique twist. This could be a ship that grows with levels like in a roguelike, various enemies with distinct traits, or special map features (galaxies, nebulae, etc.).
I think with a bit of effort, you could make a solid arcade game—at the very least, Unreal Engine allows for it :)