If CFF plays Marathon speed, its possibly realistic what she's saying I feel like. I don't think of myself as all that great at the game, and there was a small period where I could win Deity Marathon about 50%, assuming you don't count occasional ten turn in rerolls. Now, that was in part because I absolutely crushed the AI on the high seas esp once Frigates came along, which is no longer possible (at least for me). But still, there's at least some gap between Marathon Deity and Standard Deity, and anyone who complains about the AI not being to defend its cities before Gunpowder, I would guess has a lot of turns before Gunpowder to notice, and believe me, there are a lot of turns to attack pre-Gunpowder on Marathon. Also, from some logreading I've done, it seems the bigger the map, the more likely the AI is to pursue Diplomacy, which means sprinting to Printing Press, which means even more turns before Gunpowder. Don't know if that's still the case.
More on topic, if I ever get back to the highest levels, the pledge to protect and tribute change will be an absolute delight!