The way I see this: I play Civ for having a game with interesting/exciting/entertaining situations/decisions/actions. Of course, every game is played for that. Now what does the factor „Civ” mean in this? That is, what do I expect Civ to be in order to achieve all I want to have? I want experience, a special experience that will play itself and happen in my mind: I want to believe I rule and control a story of a civilization that goes through a story that resembles real human history. For this, the game needs elements (setting and plot) that invoke the reality of the history of mankind - this is what my mind needs as ingredients to make up my fantasy story during the game. Civ needs historical reality as a framework - this will make me to want to play the game, this is why I play Civ, specifically. It also needs to simulate the world and history that is the setup. But it is tricky - for I need freedom to make my story in the game, and that will differ from real history. So what Civ should aim is not realism and/or simulation as per se, but immersion, for the player to be immersed in a world that is in the context of mankind’s history and world. And for this Civ should use realism and simulation only as means for a goal. Immersion and story - these are the key points.