I think that change only comes through a big, imaginative idea
This seems overly optimistic to me. I think the historical record demonstrates that broad sociocultural change primarily happens after some great destructive crisis (war, famine, plague, etc) during which the status quo breaks down and a lot of people die, and the survivors have to pick up the remains and try to patch some form of society back together like a jigsaw puzzle where half the pieces have been burned in a fire.
Sometimes, the survivors get together and try to imagine a better future, saying to themselves, "we don't want our children to have to go through what we just went through." More often, the person or people with the most resources left after the crisis take control, attempt to form society such that it sustains and increases their current power, and repeat the same old cycles of exploitation and selfishness.