isn't it not fair that a team can make a much better game then a single person?

It's true that it isn't fair, but theres no easy way to fix that. The main point of the jam is to make things and have fun, and limiting the number of people that could work on a project would go against that. If you care a lot about winning the best move is to join a team, but in my opinion winning shouldn't be your goal when doing game jams

No one's stopping you from making a team of your own ¯\_(ツ)_/¯

it’s funny to some that people in the team don’t work, but he wrote this comment and now he has 13 ratings for his game.

Common, just relax. Jams is a place to have fun and test yourself for strength. I made the game in solo and judging by the reviews, it turned out pretty well for me. We are not here to win, but to have fun and communicate in the community.