I understand the dissapointment in the Westernized vision of the developers, and I think a strategy game that takes a different approach to history (other than imperialism, nationalism and politics) would be a nice concept, but also extremely difficult to apply in practice. At the end of the day it's a lot easier to create scores and win conditions based on the amount of land owned and number of wars won, rather than cultural and social values. Those are a lot more personal and abstract, and thus more difficult to incorporate in a tasteful way in a huge game like this. concepts like society, culture, zeitgeist, art & literature, human contacts, traditions & conventions,etc. are incredibly complex and it's practically impossible to fully grasp those concepts and feature them in your game in a meaningfull way, without causing some massive backlash. Add to that the variable of player agency and you might end up with some rather unfortunate results.

As for non-European nations functioning exactly like European ones, I think that, again, can be caused by the need to stay pragmatic. They are mostly just expansion packs, so I'd think that they wouldn't spend a lot of resources in creating an entire new system of ruling. It would be impossible to create for each "nation" (really, even countries in Western Europe are generalized in this, if you were to draw the line much further), and it would be impractical to play, since you would need to relearn the game with every new playtrough. As for being able to play them, I think it's mostly the novelty and added difficulty for more experienced players, who'd want a challenge.

I'm still under the assumption that the Eurocentrism is in the game to fully immerse the player into "roleplaying" a European ruler, rather than posing an argument about history, or providing introspection. I would fully support if one were to create a game with some meaningful insight in history, and I'm curious to what the result would be, since it would be a very ambitious project. If I have to be completely honest though, I don't see a strategy game working as a medium to deliver that message, since it's an extremely loaded subject, with a lot of nuances, and it could spike a lot of controversy if handled poorly.