A big point is made in the original series, with Scotty and Chekov, that ethnic identities, even ethnic accents, survive into the future.
Roddenberry did that as a deliberate attack on the racism that existed in Hollywood at the time, culminating in the first televised interracial kiss between Uhura and Kirk. You cannot look at Star Trek in a social vacuum and you also have to remember that the soul (first Roddenbery, then Berman and I've lost track of the newer Star Trek variants) of Star Trek has changed over its lifetime.