It simply means that there's something wrong with scaling over time. It shouldn't matter where you settle your 8th city but it should matter if you get Industrialization (or any other tech that boosts your production enormously) 5 turns earlier or not. So when in early games you make strategic decisions about city location in late stage of a game, when the map if already fully covered, you should have another strategic choices to make. And CIV always failed on this part. Like in history. Western world and Japan were first to benefit from industrial revolution and they profit to this day. On the other hand China was behind at the beginning but because it's became such a huge country it can catch up quickly now.