It's a problem all right. Game jams on itch.io can see fairly high participation, but the conversation around most entries is usually non-existent. Most people don't rate, don't comment, don't bookmark, don't nothing, as a general rule. And if someone has a solution, I'd love to hear it, because what more can developers do than, you know, participate? That's what a public game jam is for: increasing the visibility of entrants. If that doesn't work, might as well hold a private event at a LAN party.