As a user: boldly use new social networks that fit this mold and allow your social circle to grow to embrace them. Participate with the network on its own merits and the new friends you can make, not the based on whether or not your old friends are there. The only way to solve the network problem is to ignore it.
As a dev: don't build new walled gardens. Consider how to connect with the existing ecosystem - and crucially, how it can connect back to you - when designing your next project. Prefer collaboration over competition. Prefer small, interlinked communities over large silos. Distribute costs across the network, by letting volunteers shoulder hosting costs through grassroots "local" fundraising efforts.
2: Nice! It would be cool to organize a simple cirriculum for privacy literacy and start reaching out to local libraries, schools, etc, about giving talks or classes.
Re 2: I used to co-organize "privacy café" workshops. I was surprised by how many people showed up and how grateful they were to learn about really basic tools -- like ad blockers or just browser cookie delete functionality. Everyone knows how to brush their teeth, and everyone had to learn how at one point. Digital hygiene is no different.