Its a starting point for a cool game. Personally when I started doing development I wanted to work only in 2D because I understand that 3D is a bit more challenging, plus its easier to create custom art assets for 2D over 3D. Don't beat yourself up about it, the purpose of the game jam is to test your skills for where they're at, not where they're going to be. Just keep on developing and you'll get better with time!