Agreed 100%. To me, it seems silly -- not to mention cynical and fatalistic -- that the sole purpose of diplomacy in Civilization games is to add a strategic dimension to warmaking.
Out here in the real world, war is a continuation of politics, by other means.
Same thing, really, as your description of Civ II. The goal of diplomacy/warmaking is for one's side to come out ahead of the other.
See Clausewitz, Machiavelli.