You have shifted the discussion from small overlay network for friends and family to large overlay network for "millions of followers".
Those methods of sharing content with "millions of followers" are already available and will no doubt continue to be available.
A small private network is a different idea, with a different purpose. People will always have the choice of using a public network however a small overlay can avoid sending traffic through third party servers, like Facebook's.
There is no requirement that a service has to be "free", or supported by ads. This is something else you injected in the discussion. I use free software to set up overlays, but I have to pay for internet service and hosting. The cost of the "service" is not the setup it is the internet access and hosting.
It's easy for people to point what they don't like about Facebook, but I don't think you are really comprehending why they dominated the social network space to begin with. It's not as easy as making a product that doesn't advertise, if it costs money to use instead.
The problem is that no one has the incentive to host such a service for free, and users wants the content to be available 24/7. So it's not as simple as just setting up a peer-to-peer network. Users who just use a phone as their primary computer will still want to be able to publish to their millions of followers, and so it wouldn't work to have those millions of people connect directly to this person's device. Maybe you can solve that with a bit-torrent like approach, but the problem gets harder when you include the ability to send messages privately.