Maybe something like each forum only can have a few of their posts per day appear on the front page? So even if someone creates 100 posts in A, forums B, C, D, E and F with about five posts per day would still be visible.

I'm mostly looking at https://ramble.pw/all/new so I don't care too much either way, other than being interested in optimizing the front page to attract more users.

And as a new user, it would probably be nice to easily see all the forums with some activity instead of just the most active ones. But even then, should there be a point where 5000 forums are active, you again will have a hard time figuring things out.

But for now that's my idea at balancing.

Maybe the front page should even show the few posts from each forum at random. So each time you reload the front page, you get something different, if there are enough posts in the pool. Prevents gaming the front page, too. At least to a degree.