My objection to the thermodynamic argument is that it means that no value can ever possibly be gained from any action whatsoever, both at micro and macro scale. Life is pointless, nothing matters, etcetera etcetera. While undisputably true, it doesn't make for an interesting discussion.

Capitalist model, even if fundamentally wrong, at least makes it possible to talk about value and its changes. And even if it doesn't describe real world, it still describes some kind of world. Taken purely as a mathematical construct, the world of the capitalist economic model can be analyzed in terms of game theory. And at least when I do the analysis, it comes as non-zero-sum. Not only because of services, but also because of processed goods - even if thermodynamic balance is the same, some arrangement of atoms have more value than others, usually because of their utility (copper lumps vs. copper wires, for example).

Taking away parts of the model in order to show that it's zero sum isn't very convincing - what if it's only zero sum because you took away parts that make it non-zero-sum? A much more convincing argument would be to add to the model - accept what the economists say as is, but expand on how externalities are being ignored and that if you account for them, the sum does indeed end up zero.

Note that I'm not claiming capitalism is good. I'm only claiming that in game theory terms, it is not an example of a zero sum game. The only way it could possibly be true is if there was some inherent law that any . It's much easier for me to believe the world will be destroyed in 30 years due to capitalism than that the world being eventually destroyed is a mathematical consequence of zero-sumness of capitalism.