A little :Late: but the nearly twenty-year old Realism Invictus mod for Civ 4 had a pretty major update last year:
https://www.moddb.com/mods/realism-invictus/news/realism-invictus-37-released
Modding is the sole reason I still place Civ IV as my favorite in the series, it's a shame Firaxis didn't take more concepts from that mod instead of ripping off Humankind and Age of Wonders.
Representing a civilization as the people but changing the flavor based around the government choices you make added much to differentiate between your dudes as time passed along, even if it was just a name and a new flag almost all the time, it showed real progression.
Going from "Frankish Tribes" (start of the game) to "Frankish Kingdom" once more organized to "Kingdom of France" with some kind of feudal civic/policy, and carrying on to a French Republic, the Avingion Papacy, The Paris Commune, the French State, or the French Empire depending on the government, civics, and tenants you go with.
You don't have to copy that system bit for bit, but judging by the success of paradox games, people are suckers for some flavor and role-playing in their map games. Switching from one civilization to another entirely from era to era is not only largely nonsensical, but unoriginal as well.
I saw the art style of Civ VII and it looked promising, but nonsense like Harriet Tubman as a leader and the game ending around AD 1960, as well as a lineup of ten civilizations to start with, a lower number than Civ I's fourteen. This seems like an odd way to combat Civ's "peaking" when they can roll out a really good Unique Unit or Building, a system present since Civ III that nobody had an issue with.
No England, No Scandinavia (ik normans encompass both but eh), and of course the great Red-Placement continues with no Celts. Civ VI launched with
thirty-four civs, with the worst omission being the Turks.