To give credit where it's due, and without overstating it, just look at most of the science fiction produced before and since. Uhura and Sulu may have been "tokens" by modern standards, but at least they were there in the future--which is more than than you can say for most of the classic sf films and tv series of the fifties, sixties, and even the seventies. Look at Forbidden Planet, The Thing from Another World, IT! The Terror from Beyond Space, Lost in Space, Logan's Run, and even the original Star Wars. There's nary a non-white face to be seen in any of them, let along respected Starfleet officers exploring the universe of the twenty-third century.
As I mentioned recently in another thread, not too long ago I was watching THE GREEN SLIME, a "futuristic" scifi movie, set on a space station, made a few years after Star Trek debuted--and, ohmigod, it clearly never occurred to anyone involved in the production that the future would not be run by rugged, white American males--and that women would be anything but secretaries and nurses who screamed and panicked at the first sign of danger. Trust me, STAR TREK looked positively "revolutionary" by comparison.
Trek's efforts at diversity may have been sometimes been a case of two steps forward, one step back, but at least the show was consciously making an effort to present a future that didn't look like Mad Men in space.
I was watching "Court Martial" again the other day, and couldn't help noticing that, beyond Commodore Stone, there's also appears to be an Indian officer on the tribunal and an Asian woman, identified as the head of the Enterprise's personnel department, among the witnesses, all of which goes without comment. Not bad for a sci-fi show in 1966!