Well, we can see that the game’s name is Civilization, not Western Civilization.
I certainly wouldn’t buy a game where every square kilometer of Europe was a civilization and the entire East was reduced to just half a dozen civs.
The greater mediterranean area probably should have the highest amount of representatives, proportional to the amount of available slots. The region was a hotbed for empires, with many unique culturally distinct civilizations. (I include both Europe and Mesopotamia into this area btw).
Also, nearly all of these cultures left written records and were generally well-attested.
There probably should be more European civs than what gets shipped at launch, but not many more. It's more that two 2 Per era is a low number because we already have a large amount of western leaders -every one of them defaults to Rome or Greece and it would be better to have a third option available for them to pivot from (Gauls, Goths, Norse) and into (HRE, The Rus', Byzantium)
Additionally, if you look at the empires outside of Europe - they were HUGE. The Mongol Empire was HUGE. The Achaemenid Empire was HUGE. China is HUGE. Russia is GIGANTIC. In those areas, the amount of Civs you can represent per square area is low (but the flip side is that most can be represented across all three era's in a more or less straight line.)
Now I'm not defending anything a
specific person here has said. Nonetheless, to have more "Western" of "Middle-Eastern" civs makes sense from a designer perspective. Well-attested Civs, recognisable Civs, and just the sheer amount of Civs available will all factor into that. The effort the devs have to put into delivering something like the Shawnee (and it was a MASSIVE effort, especially for a DLC Civ) cannot always be replicated. If you're making a left-field choice, like Shawnee, you should make it count. Which makes such civilizations quality-over-quantity.
(and point/counterpoint is Isabella's Spain which barely feels like Spain (especially
when led by Isabella), and Ming which feels a slightly less boring version of Civ6's Korea)