Reading your page it seems like you've learned a lot of new things which is great. Obviously its resulted in a somewhat unfinished product but learning cool stuff is its own reward.
I like that you went with the parallax although I think I would have had 1 layer constantly moving as you're never really stationary in space and I think maybe the layers were too tight, I don't know if there were too many or they were just too close in "distance".
I personally didn't like the ship controls, it was very difficult to manoeuvre but I appreciate that is a choice and preference thing.
I did have some issues with the WebGL - I don't think the unity and itch.io full screen buttons play nice with each other, I would try turning off the itch.io on , even in full screen some of the text at hte top was cut off.
Theme-wise, I think this is probably one of the most shoe-horned games but themes are hard, you got a game out and it is playable. Visuals were great and the music was very nice.