Tough. You would have to score with engaging game play and or story. Baba is You is already invented, but that had quite non eye candy graphics. It can be done, but people will see the thumbnail of the game first and this should appeal to them somehow. Eye candy is easy. Horror is popular. But appealing to the puzzle-senses if you make a puzzle game or appealing to the adventure senses if you make an adventure and so on, might be achievable.
The most popular game ever, Minecraft, has horrible graphics.
So the theory is, that bad graphics are not a roadblock to success. But they might pose a hurdle in the beginning.
I do not really understand jams, but I suggest you should make a topic here, if you host another jam. See, if people are interested and why, or why not.
If you seek inspiration, make a jam about games that have no graphic artist on board ;-) Maybe with the twist, that it has to be a game where one normally would expect nice art. No AI allowed of course and no standard assets. Jams are among other things about learning as a game dev, are they not.