Congratulations to your first jam! This game has really cool looks and a banger music!
This is my first jam as well, and there is one thing I learned which I would like to share with you: Since your controls are pretty unique, maybe you should include a warm up phase where you don't get killed right away while you try to figure the game out. You could even consider a separate, easy level starting to introduce, step by step, the different features and movements. It took me a while to figure out, others might give up earlier. Also, for the first ten games i wasn't even sure if i hit the right button, there is so much going on that you don't really know if you have control over the chaos or not. (don't get me wrong, i like the chaos a lot :D)
As for the display, it is difficult to get it scaled correctly, i see most of the screen when i zoom in, but not all, i don't know Godot so i don't really know how you can improve that.
Overall, i think that the spawning cubes and change of active player idea is super fun, it is sort of a swarm feeling, really cool! In my opinion, worth polishing.
Maybe you can add a endless runner (or endless faller) mod as well...