While I am having trouble understanding the complete game loop and why simply stacking "attacking" nodes is not optimal, I feel there's some great potential in there! Allowing player to fully build their own "defense AI" with such a branching upgrade tree looks really cool!
At some point, a small tutorial would do wonders! But not having is completely understandable for a game jam. We also didn't find time for it. :D Never enough time!
Good job!