I'm not against you or your idea, im just extremely upset you're coming here 2 days before the jam starts and want to give a new approach to the theme selection. I'm sure people didn't just get into the jam and were like "see you in a month!" No, they took the jam themes, the possible themes and studied them and thought about ideas and this and that and yadda yadda yadda.
Don't take me wrong, I would totally go with your idea of making the themes less generic but right now its TOO LATE for that... Yes, it's true that gamedevs gotta be ready to come up with an idea in a short period of time but why make them do that when the initial idea wasn't even that?
If you suggest something like that so late, suggest an additional rule, DON'T suggest a complete change 1 day before the jam.