I think it was just a design decision to make the ancient era involve a lot more fighting. You can see it in the way warmonger penalties work and the increased power of barbarians. It's logical that in the first few days people play this game like it's civ V and get punished for it. That said, when you get an unlucky with horse barbarians it really does get difficult. Once you've got a decent military established you can switch your focus to the economy. It's nice to see that the AI does less wonder rushing, or at least it seems so. That way you don't completely have to gimp yourself in the early game to get one.