Thanks for playing! I agree with you, I should have spent some time balancing the game, but I downloaded Godot on friday for the first time, so thats everything I had time for.
As you mention, the collision shape of both player and asteroids is too big, and I also noticed that the asteroids should be smaller in general. I should've added the possibility of moving backwards as well, or make the 'gravity' bigger.
The reason why you can get trapped is because difficulty increases every two seconds, adding some asteroids to the spawn loop. As I couldn't spend time in balancing the game, I think this might be a game-breaking feature