The whole point of this, and too many other pointless threads on this Forum, is Immersion.
And the reason it is pointless is that it means entirely different things to different people. In fact, no system of any kind will appeal to everyone, and a system that appeals to only one person is just as appropriate (for that one person) as a system that appeals to hundreds of millions.
Some people Immerse themselves in a Civilization, 4000 BCE to 2025 CE.
Others Immerse themselves in a named Leader.
Others, frankly, don't appear to Immerse themselves in any thing other than beating the game's mechanics as fast and efficiently as possible.
All and many dozens of other different examples a re equally appropriate TO EACH INDIVIDUAL GAMER.
So, with all due respect, you all keep arguing about the numbers of Civs and Leaders that can dance on the head of a pin and whether they should be dancing a tarantella instead of a fandango, and I will go play Civ VII as Charlemagne of the Mayans using an ancient Xiong-Nu city list so that I can easily advance the Civ into Medieval Bulgarians using an ancient Slavic city list in my own little personal Immersiveness . . .