What if there isn't a "value proposition"? Some times the value comes from people using it, and people find their own value in it organically. With forums, if people use it, it has value.
The nomadlist slack is effectively a forum in this niche that's a lot more active, and people tend to follow the rules because you have to pay $100-$300 to get in. Not really sure it's worth the money though. I do like the idea of accounts having a cost so the service can pay for mods & hosting, but the price is a bit steep. Something in the price range of something awful forums might be better, because there's a lot of real nomads who wouldn't pay $100 just to get in a slack.