You're being uncharitable, which is part of the problem. These supplements
are "recently invented" in terms of evolutionary history and it's not clear how well they work, compared to actual sun exposure.
"Not suited to" may be a contentious choice of words, but "not adapted to" is plain fact. Not being adapted to an environment confers disadvantages. Perhaps these disadvantages are minor, certainly in this case they are not lethal (in isolation), but from a healthcare perspective, they are important to take into consideration.
Consider that jumping at every opportunity to scold someone choosing their words unwisely does nothing to actually fight racism, but could indirectly harm those people you are intending to help. After all, why would a true racist care about the health outcomes of the races they ostensibly despise? Why would anyone risk investigating genetic differences in medicine, when the payoff is an accusation of racism by well-meaning but uneducated laymen?