Make sure that your game starts and correctly scales to the viewport.
Make sure that the game you uploaded to itch.io actually *starts*.
Make sure the potential player doesn't need to download Java, Python, or whatever in order to run your game.
Make sure that the controls are documented, at the very least in the description, but ideally in game.
If you fail at one of these points, people are unlikely to play your game, let alone rate it.
Making mistakes is human, but if you made any of these, learn from them for the next time you do a game jam.