Collectivism is really the domain of the small.
https://en.wikipedia.org/wiki/Small_Is_Beautiful
For human beings, the number where a communal understanding can work and seem like magic is about 350. The missing key to understanding this, is the network of interpersonal relationships that form in any society. These networks are like strong fibers in a composite material, giving it a cohesion and tensile strength that the aggregate wouldn't have otherwise. Those who operate small companies know this firsthand.
A lot of collectivism is akin to selling concrete by advertising using the specs of reinforced concrete. It doesn't hold together as well as it should on paper, because there is something very important missing in the theoretical description. For larger numbers, in the millions and beyond, there needs to be some kind of larger organizational structure. Historically, this has been hierarchical, but other solutions could exist enabled by technology.