Solve for status and affiliation
Status and affiliation. Those are two things you can solve for.
Surprisingly (or not), people are concerned about how whatever they do affects how their status and affiliation are perceived.
Rather than complaining that it makes others selfish, why not solve for that?
Why not build that into the core of the problem you are trying to solve?
What does it feel for others when they are part of what you are building, or what you just built? What does it do to them, and for them, when they tell others about it?
It's worth thinking about. Because, in some ways, it’s inherently human.