Neither the units nor the tech tree is designed to provide a gazillion civilizations and keep them unique at the same time.
Even before the expansion, I have claimed that the game will go downhill the more civilizations are added. And the new expansion showed who turned out to be right. You get nothing but the dilution of the uniqueness of the original civilizations, gimmick mechanics, power creeps, and endless things to keep track of.
There are already several similar civilizations, and it should have been enough for some people to realize that adding more civilizations to the base game is a dead end.
It’s not like some very impactful medieval civilization is still waiting to be added. Because they are already added.