AGAIN, there is no chinese empire, there are several chinese empires, with unified china being a hegemony. If paradox thinks that only China, India, and Rome are worthy of being hegemonies, then Vietnam can have an empire (of roughly modern borders), and still be outside of China's hegemony.
I think we should discuss based on specific facts. Obviously, that's how Paradox did it.
If you express an inappropriate opinion, you should present your specific facts, and then we can compare the facts.
You cannot simply infer the situation 1200 years ago based on modern national concepts.
Moreover, you may not know that the "YUE Empire" in the game is within the territory claimed by the Vietnamese people today, because the "Nanyue Kingdom" advocated by the Vietnamese at that time was the origin of Vietnam, which was a colonial country established by General of Qin empire with its capital in Guangzhou. (During the Sino Vietnamese War in 1979, this was also political propaganda on the Vietnam side.)
In Vietnamese, vietnam's 【viet】 means 【yue】, which is the name of the "yue empire". Nam is nan, you can try pronouncing it, it's just a different expression of the same Chinese character between two different languages.
Vietnamese people claim Chinese territory, call themselves Chinese, and have ambitions to tame dragons, which is a historical fact.
Perhaps you just can't distinguish between the north and south of Vietnam?
Because the Champa culture in the south belongs to another cultural circle, they do not have much to do with China, and they should indeed belong to another empire outside of China.
But in the year 867 when our game began, the Vietnamese did not advance into Champa. In 1066, the Vietnamese had just launched their first expedition to Champa and were unsuccessful.
Vietnam completely occupied Champa in 1402, when the Middle Ages were almost over.
So in the process of our game, Champa's influence has not yet affected Vietnam. Vietnam does not have a Southeast Asian origin, and their focus is on the north rather than the south.
I have emphasized many facts to you, and you can find them on the wiki encyclopedia. I hope you can also present your own facts.
I hope this is helpful to you.