When I say "any system imaginable" I mean his tendency to elevate the social/anthropological realities over the other realities: that if we can plausibly believe people could act in a certain way (and there's so many possible ways) then they can make it real in a world of real physical and informational limits. I think he takes it way too far in this sense.

Reciprocity is a perfectly good way to run a small economy. But note - you're still trading, in a significant sense. Accounts of who does what are kept, the relative value of items and acts are considered, and social honor and reputation are valuable goods in themselves (in a "capitalist" system as well.) One does not escape from "markets" or "property" just because some goods are social or symbolic.

I agree we've sort of ended up at different destinations. I'm aware that "global capitalism" is a strange beast - but not really any stranger than anything that's come before. It's sometimes hard, but works okay, and is probably worth keeping around on its own merits.