I think part of the problem is that we migrants decided that each reddit community also needed a corresponding lemmy community right out of the gate. For example, on reddit, there is r/hockey, then there's a sub for each individual team. However on lemmy, the team subs are dead due to insufficient traffic, and stay dead due to the exact chicken-and-egg problem you describe. The solution is to congregate in a larger community instead, where traffic is higher, even if you're posting about your relatively popular game. So as a Winnipeg Jets fan, I should post in the lemmy hockey community and not the Jets community. Likewise, if you want more chatter about Cyberpunk2077, post in the general gaming community. It works reasonably well for now, and if the signal to noise ratio ever gets bad in the larger community, then you can split off into specialty topics.

Ironically, reddit also went through this exact process 10-12 years ago. r/science became too noisy, so people ended up in r/physics and r/chemistry, and r/askscience and such. We need to start with communities with larger scope until they're active enough to split.

At this very moment I'm looking for a discussion on sci fi oriented table top rpgs. On reddit, there is dedicated discussion forums for a few of them. Here, I'll post to !rpg@ttrpg.network because there's more people there. Off I go!