I get your point, but I don't think a board game is a good abstraction to collapse the real world into. The world is not a fixed, closed system with finite resources. In a board game, expansion and innovation are not possible, only trading and strategy, as you mentioned, can optimise the system to some extent. Moreover, winning in a board game happens solely because of its rules, whereas in the real world, one person's success does not necessarily mean another's loss. Trade can be mutually beneficial, driven by each party's ambitions.
Innovation is an interesting wrinkle in the comparison for sure (I used the comparison only to continue with the previous commentor's point). Innovation only increase the potential usefulness of resources though. Assuming that will always avoid hitting the boundary of the zero sum game assumes perpetual innovation at a good enough pace to keep up.
Trade is an interesting one because it can be mutually beneficial, though it rarely includes everyone. Two countries can trade and both be better off, but other countries excluded may now be worse off. Trade also can't be mutually beneficial with regards to relative gain. Both sides can gain in trade or cooperation but one will always have gained more than the other. That doesn't make my point by the way, but an interesting related dimension to the whole topic.
