The fediverse is a step towards p2p but there is further to go before "anybody" can pitch in resources. Running a server is not for everyone, I've done it and won't do it again (I've been doing this stuff for a long time BTW).
This creates an imbalance been those running and controlling servers and those not, which has a number of downsides which in the extreme lead to capture and centralisation. The fediverse is a fantastic attempt to reduce those downsides (FOSS, portable accounts etc) but the server/service model remains at the core of the downsides including as the OP asks, how this can be funded and sustained.
IMO the fediverse will struggle to do this at scale. It is here to stay but will find it difficult to reach so many of the population because while small it remains separate, and where it scales sufficiently it becomes attractive for capture and centralisation.
So IMO we need something that breaks from the server model as well as solving the problem that not everyone can contribute resources, and I'm hoping p2p projects can do that.
If there was a p2p network where anyone can contribute resources just by running an app, and anyone can use by paying those running those apps, I think we would be able to have the nice things we want - at increasing scale - without fear of capture, and the real prospect that everyone can participate without being made subjects and exploited.