The voiced quotes for each tech in Civ V were downright haunting for me, and I'm pleased to see the game kept so bright. Even the military quotes strayed to optimism like "Happy are those whose walls already rise."
Sid Meier gave a talk at the GDC: https://www.youtube.com/watch?v=MtzCLd93SyU
In it he explained how Civilization tested random negative events that could shape your world. He mentioned how this had a negative effect on the player experience and many times people would just grab a past save to avoid them IIRC.
I would actually disagree. There are plenty of power fantasies, most notably the spectacle fighter genre, which seek to make you feel powerful. Civ isn't about that.
Civ makes you feel purposeful. You nurture and grow your civilization, not for personal aggrandizement but for a feeling of progress and accomplishment. Your goal is not to be the most powerful ruler, but to have the greatest civilization. Human achievement and ambition is the theme of the game.
Well, knock the population down. How? Either raise taxes until they revolt and then put them to the sword, or move plague carriers into the city to keep things in check.
That was a properly dark game, and I'm glad Civ isn't.