The idea makes this game very unique, I'm impressed that a first JAM could turn out like this !
Of course as you mentioned it's not perfect but in the end what really matters is the idea of your game, what will make your team grow is experience on other projects. As long as you keep on being this creative, all that's left is finding a nice workflow and find time to polish mechanics.
Here's a few things you guys could do before participating to a new JAM or creating a new project (I'll be talking about platformers but you can extend it to other genres):
- Play a bunch of other platformers and figure out what works, what made it frustrating sometimes but more importantly what felt good, what made you stick around (++ Game design)
- Go check out a bunch of videos of the GDC, that's a very famous source of data and expertise, they have a great youtube channel (every skills)
- Try looking into game architecture and software architectures, it will help you build modular games, which will help in making bigger games no matter the time constraints (++ programming)