Yes why it's an issue for something to ever be all white is beyond me. When something is all black or Latino or anything else, it's "diversity." When something is all white, it's "homogeneous" and "segregated."
Man if you are a black or Latino actor or model with the slightest bit of ambition, there will be some work there for you since there are so many advocates for you. The same is true for minorities that want to go into any field. For every young pretty white girl that was picked for this issue there are literally hundreds that are waitressing, working for promotions companies, etc. just trying to scrape by a living with the dream of hitting it big.
Nobody is eager to make sure hard working young white men and women will be able to live their dreams. Only they can live their dreams with a ton of persistence and a little bit of luck. It's completely insane to think someone who has put in so much effort to make it to the top, i.e. landing a gig like being in Vanity Fair, should be caste aside just to put a black or brown face in there. The sad thing is that there are many white people who say they agree.