In the future Star Trek wants us to imagine a black female officer is completely unremarkable.

Interestingly, in the unaired TOS pilot Pike did in fact remark on a female officer (albeit Una rather than Uhura), saying he "can't get used to having a woman on the bridge".

Of course, being unaired, the episode's canonicity was pretty questionable. Until SNW used the exact clip of him saying that as archive footage.

(n.b. None of this is intended to negate the point you're making. It's just a strange little thing that could have been brushed aside as an artifact of the show not quite having figured out what it was yet, had not modern Trek gone and affirmed it.)