Absolutely not! They are totally optional.
But we encourage you to enter for a few reasons, even if you don't think you're good enough to win:
1. It's fun and helps you push yourself to get better every time
2. It's super educational to compare your mixes to the other entries and learn about your own strengths and weaknesses as a mixer
3. Who knows, maybe you're better than you think?? You could surprise yourself and win a cool prize :) You'll never know if you don't enter!