...I am convinced that decentralized/voluntary/anarchistic forms of societal organization are far superior to centralized forms in terms of their efficiency...
This is not, nor has it been in recent history, a reality. The fact that such arrangements have never persisted is, in itself, proof of their implausibility. A world where there is no crime, for instance, is superior to a world where crime exists. But such an ideal is as implausible as the utopian volunteerism you describe.