The Soviet Union “diverse”? I guess they had a bunch of gay composers and ballet dancers, but their blacks must have been really light-skinned.
The Soviet Union was in fact the most diverse nation by ethnicity. Look it up in the internet, doesn’t matter where. Russia today is still one of the most diverse nations of the world.
Russia is still a very diverse nation. There are something like 35 or 40 distinct ethnic groups composing Russia.
There may not be many 'blacks', or more properly negroids, but that doesn't mean they aren't diverse.
L