an old friend answered this the best imo. so i will just link to her post
but i will add that what you are actually saying is that there is an equivalence between alliance high elves and blood elves. when really alliance high elves are what they seem to be, relics reflective of the tiny number of thalassian elves that did not remain with their people as they joined the horde and sought refuge in dalaran under vereesa and formed the SC(which is still a tiny militia). adding weight and gravitas to the overall story is fine, but extrapolating that to becoming playable is where i, and apparently development, draw the line. we need alliance high elves as much as we need horde humans