In short, I think the effectiveness of altruism is limited in a non-demopistic society.
My perspective is that markets are a key factor in enabling things to happen. EAs are focused on promoting the social good, but current markets only promote individual benefits, not public benefits. We can either work upstream against the structure of incentives that currently exists, or we can implement systems (such as Quadratic Funding) that align incentives with the public good, thereby making our work easier and motivating more people to work on projects that the EA community values.
But we can decide what goes inside the machine, whereas with people we can only control outside circumstances. It seems to me that such a mechanism would be highly likely to be an internal mechanism, so wouldn't be applicable to people