Not sure what you mean by "natural." The cast of characters in a television show are completely artificial constructions.
As in "flows naturally from the writer's concept of the character", a weaker, but legitimate, use of the word than the literal "created by nature". I get your point (I even commented in the post to that effect), but there seemed no better way to phrase it.
You are absolutely right, statistically we would expect to see very few white males in that position and it makes it unrealistic to portray it that way. My argument however is that it does not follow that we should therefore apply a formula to extrapolate exactly what ethnic/cultural/gender mix to expect and then shoehorn it into the show.
A well written character does not start as a set of demographic labels which then gets a name and rank attached, they are created as a rounded person who originates in another (real) person's head and develops from there with their sexuality, race, gender, etc being a part of that progression. They are not defined from the word go by those factors.
How isn't "everybody's white" not a quota system?
They aren't, but just look at two contrasting examples of non white characters we do have:
Sisko: a thoroughly examined protagonist with flaws, doubts and foibles that make him very human. He is constantly beset by anxieties regarding his past losses, his actions, their consequences and the role the future holds for him. We go on that journey with him and become intimate observers of his transformation into someone who can face enormous responsibility precisely because he has faced his demons. In doing so we humanised the predicament faced by the wider society of the federation of how to reconcile ideals with necessity and live with the fallout. He also happens to be black.
Travis Mayweather: token black guy. Has such classic dialogue as "passing warp five now captain!". The constant butt of jokes in fan circles for playing virtually no part in the show and possessing zero personality, despite having dozens of hours of screen time. Not because he personally lacks charisma (that could have been used by a good writing team), but because no one actually cared enough about the character to make him frankly noticeable.
See my point? One is a character who is iconic amongst the fan base and deeply loved because he was so well written from the ground up, the other is just a space filler that puts a particular demographic on the bridge. Great characters and by extension great stories come from the former, non entities and therefore mediocre, meaningless stories come from the latter.
Granted the numbers are askew and could probably be made more realistic and I would welcome that, but not at the expense of quality writing. When you ask writers to start from the word go constrained by a numbers game you are tying their hands and by extension lessening the value and impact of their creation. Star Trek has a proud history of being a parable, a tool for social change, but the days of doing that at the casting stage have gone.
Far more impact could be made by giving the writers a free reign and allowing them to write thought provoking, relevant stories and expand the ST universe in ways that challenge preconceptions about their world and thus our own without making it a mathematical exercise much like every other show out there