Your imagination of self sustaining communities is distorted.
I guess it depends on a person's view of self sustaining community.
My view/definition of: sustaining community:
They need nothing from outside of their community. They make, build, grow, and produce everything they need in order to survive.
I just do not see that ever happening. We do not need self serving self sustained communities. What we need is a self sustaining planet.
I totally agree with you. Meaning of phrase 'Self sustaining' is different for everyone of course. What I mean by that is in beggining at least few communities that are close to self-sustaining. Then they can trade food or whatever. More of those communities, the more we gonna be free. In the end self sustaining planet.