In history elves have been described as fair skinned, beautiful and pure, implying that anything other is impure and not beautiful.

Elves seems to have originated from European culture, and unfortunately Europe was horrible to anyone with dark skin, which is highly likely why elves didn’t have darker skin complexions to begin with, as it was seen as impure.

Blizzard likely didn’t think further on this as they created lore, and went with what was the typical elven description. After all of these years of continued injustice towards people of color, blizzard have likely realised that the “pure and beautiful” description of high elves doesn’t hold up any longer, as any skin color is beautiful in its own right.

So maybe Blizzard didn’t change the lore, they just adapted it more to reality so it wouldn’t be false information, as people of color are just as beautiful and pure.