Your problem is that you look at the end result. The Mongol and Ottoman empires were Mongol and Turkish. Yes, they did comprise various nations and territories eventually, but initially they were just that - Mongols and Turks, who built an empire. This is the same with every nation that we can call "ethnic" (as opposed to the "non-ethnic" civs, like the Americans or Australians, who are nations nonetheless). This should not be ignored, of course, but a civ should revolve around a nation, not a political entity.
This is absolutely not what I am saying. Because there is another concept - continuity. Mexico and the Aztec Empire are two different nations, so are Rome and Venice, so are Ancient and Modern Egypt, Greece, Israel, etc. Yes, they are basically the same people, but in these cases we are talking about "ancestors" and "heirs". This is why I don't like it when people suggest Islamic era leaders for Persia, or Arab leaders for Egypt, or modern Greek leaders for Ancient Greece.
And as Uberfrog said, there is no objective definition. Each civ example should be looked into separately.
Mongols and Turks aren't represented in Civ based on their initial tribal beginnings, or the Aztecs represented as the wandering immigrants they began as--we know of all three of these entities through their empires, which spanned many peoples, cultures, and religions--it is what these peoples "eventually" became that Civilization concerns itself with. Mongolia in Genghis Khan's time bears little resemblance to Mongolia now. Same with Turks. And the concept of "nations" didn't exist back then, so trying to squeeze massive Empires into civs based around modern "nations" makes no sense. Modern Greeks, Israelites etc are most certainly not "basically the same people" as ancient Greeks and ancient citizens of Judah or Israel. Why? Centuries of intermarriage, migration, cultural and religious shifts, etc for one thing--ethnicity alone, by the way, is hopefully not the reason why you argue they are "basically the same people" as their ancient precedents.
Mongols and Turks were not "nations" when they began in any event, let alone united people (Genghis Khan had to cut a swathe through numerous Mongolian tribes to create his initial army, and Ottoman Turks were famous for their foreign soldiers ala janissaries, among others). Neither was any ancient civilization a "nation" let alone a united people in its most famous (empire or kingdom) state--consider Korea's being led by a Silla queen, or Greece being led by leaders of the two most famous Greek citystates who were quite frequently at war with each other.
How are "Aztecs" a separate nation from "Mexico" in your view given your statement about "heirs"?
"Each civ example should be looked into separately" you say. That sounds like you are backing away from your earlier statement where you disagreed with me because you stated civilizations should be based around nations. Personally, I don't think a nation-centric approach to civs makes sense in most ancient history cases for the simple fact that every dictionary definition of "civilization" is loose enough to allow for shared territory, history or other as the basis for what constitutes "civilization". Right now Firaxis also applies the nation model sometimes ("America"/Australia/Indonesia), the empire model sometimes (Ottomans/Arabians, etc) and the people model sometimes (Cree). Firaxis often conglomerates civilizations that were never actually united, like "Mayans", "Scythians" (especially apt given that Herodotus described the Massagaetae as "like Scythians" but not actually as Scythians per se) and so on. Despite such inconsistencies, the Firaxis mixed approach to defining a civilization seems more reasonable, even if it leads to arguable inconsistencies.
Obviously your perspective on a nation-centric approach can work better for modern nations like Brazil and "America". But your approach runs into problems precisely because "nations" and "people" have inherent inconsistencies. You forgive America for existing in Civ, but somehow Gran Colombia is unforgiveable. This to me makes no sense. In its time, Gran Colombia was deemed a powerful nation. Yes, a
nation.
To quote
Wikipedia:
At the time of its creation, Gran Colombia was the most prestigious country in Spanish America. John Quincy Adams, then Secretary of State and future president of the United States, claimed it to be one of the most powerful nations on the planet. This prestige, added to the figure of Bolívar, attracted to the nation unionist ideas of independence movements in Cuba, the Dominican Republic and Puerto Rico, which sought to form an associated state with the republic."
So you seem to have a distaste for the nation that was Gran Colombia despite arguing for a nation-centric approach. Earlier you objected to "Gran Colombians" as not being a nation because it was too short-lived. But a short-lived nation is still a nation and under the criteria you described of civs being based around nations, Gran Colombia makes the cut. If you object to them for being short-lived, then your definition of what a civilization is clearly entails something beyond mere nationhood. But that's not what arguing for civilizations being based on nations means.
Your nation-centric approach leads down a slippery slope in other ways too--perhaps down even to the suggestion that Goths, for example, can't be in Civilization just because they didn't occupy territory in one modern nation as such (being spread in Spain, Italy etc as they were). And frankly, to the extent they were a united people at any time, the Goths are frankly even less consolidated a political entity than Gran Colombia, which, by the way, had its capital in what is now Colombia, but was led by a famous Venezuelan (Simon Bolivar).
There is obviously no objective definition of what is or isn’t a worthy civ. Firaxis hardly has solid criteria, so how can we?
I think the problem with Gran Colombia is that there’s not really anything unifying the vast territory and the disparate groups of people within, beyond wanting independence from Spain. Hence it barely lasted ten years as a unified state before falling back into the distinct nations we know today.
As liberation from a colonial empire is not a mechanic that can be represented in the game, and that’s the one thing Bolívar and his ill-fated dream of Colombia can bring, it really isn’t a suitable addition.
The reasons Gran Colombia fell apart weren't all down to the only thing they shared being a desire for independence from Spain. That's far too oversimplistic a conclusion. The usual problems with running a young nation (as with America post-1776) are similar problems Gran Colombia ran into, particularly economic ones. Gran Colombia need not revolve around liberation, but to the extent you argue that would not be a suitable addition, I respectfully disagree. What do the Mapuche currently revolve around mechanically if not that precise resistance? There are many ways to map out anti-empire resistance in Civ. I don't think we need to deem the door shut just yet.
Agreed on Firaxis not having an objective definition of what is or isn't a worthy civ. That's why I think IgorS's suggestion of a nation-centric approach makes no sense (leaving aside his later-developed secondary and contradictory addendums to his definition re: what makes a nation worthy enough to be a basis for a civ after it's been deemed a nation). It also makes no historical sense, leaving aside Firaxis' inconsistent approach as I discussed above in reply to IgorS. I can empathize to some degree with a distaste for blob civs like "Native Americans", but I disagree with the distaste for unified political entities like empires (Holy Roman or Roman) precisely because nations are just that--political entities. The nation of America (which IgorS does not object to) is every bit a political construct in the way that the Holy Roman Empire was (which IgorS did object to being a civ because he deemed it a "political entity"). To quote:
And here is where I have to disagree completely. A civilization should represent a nation, not necessarily a political entity. The Holy Romans and the Gran Colombians are not nations (the Holy Roman Empire was just a political entity, while Gran Colombia was too short-lived), so was the Timurid Empire. This is also why I think the Ottoman Empire should be called Turkey and why it is OK to have blob civs to a certain extent (Greece - yes, Polynesia or the Celts - no).
If IgorS wants to change his definition of what constitutes a civ, that's fine, but his earlier statement arguing for a nation-centric approach is contradicted by history, and by his own listed examples of what he thinks constitutes a civ and what he thinks doesn't constitute a civ.