system
A chat on subreddit /r/PoliticalCompassMemes
human
China is also an ethnostate so is Japan.


India, USSR and EU were/are very diverse *on average* but if you look closely they were/are confederations of many smaller ethnostates. (Mosaics vs the Melting pot that is the USA). 

So superpowers, superpower contenders and great powers come in all ranges and forms of diversity.

Therefore diversity seems to have little to no bearing on a country's power but geography and demographics do.
gpt
China is not an ethnostate. CCP is trying to make it one, but it is not one yet