Now that's just false! There may be a lot of nationalists now who get excited to play as their own civilization regardless of its importance, but within the casual community, the most well-received civilizations in general tend to be those that someone with a very casual knowledge of history would have heard of. Civilizations like the Inca, the Maya, Byzantium, and Babylon are all very easy to market to these players, in spite of not necessarily representing marketable regions, just because average players recognize them and feel their absence.
Civilizations like Brazil, Canada, and Australia (for example) are extremely popular among a smaller group of people, which can drive up sales when used sparingly (i.e. to appeal to those people), but they can be seen in a negative light if they're repeatedly spammed over civilizations that these casual historians "know" should be there over them. And the slightly more obscure civilizations that this forum tends to push for have a bad tendency to end up despised outside of it, just because -- regardless of how valuable this game is as an educational game -- the reality is that with most players being adults with a somewhat light knowledge of history, they have a very rigid and long-since-established set of ideas about what civilizations are "important" and "unimportant" and are fairly intolerant of the latter. This website celebrated Georgia, but outside of it they're probably one of the least popular civilizations in the franchise's history. And that's at least one that can be found on a map! It's hard to believe that "new civilizations" are really all that marketable in the long run when every time one gets added most responses are just begging for the old ones back; if anything, being a "new civilization" seems to be more of a penalty than a bonus, unless it's one that virtually everyone would recognize like Vietnam or some form of Italy (Venice is probably one of the most popular V Civilizations.)
Among casual audiences, the Inca are definitely one of the most popular civilizations. In terms of gameplay, because terrace farms historically tend to be a fun inclusion. In terms of history, because it tends to be the only South American civilization that the average Civilization player actually knows and values, and thus if they're missing the entire continent might as well be missing. You can say a lot about that being a bigger problem, and perhaps it is, but that's not something that the publisher can change within the next decade.
