To delve into this more, I would say you do need a group of people that agree to a certain vision or goal. Yes. But I have no clue yet how to work around finances. Money is difficult because for some it means getting medicine and medical care they might be able to get within a group. It means having to navigate two worlds essentially, capitalism and the world you're trying to create where that doesn't exist. So I think accessibility, financial organization, and diversity need a big overhaul.
Sunbeam City is a anticapitalist, antifascist solarpunk instance that is run collectively.