[Disclosure: I'm an entrant in the comp]
Where I've come across something like being asked to rank puzzles in a puzzle-less game, I've been rating it 3 stars as "neutral": it neither has shiningly awesome puzzles, nor is it trying to do puzzles and failing. (I'd leave the score blank if I could, but I don't think itch allows that.) Others might not see the point of a game without puzzles and rate it 1, or be refreshed at not having to do puzzles at all and rate it 5. Their choice.
Note that (as I understand it) only the "overall score" ratings count toward the final results of the competition, so you needn't worry that you're unfairly lowering a game's score.