Hot take: where Blizz shot themselves in the foot with this was the introduction of Void Elves and Lightforged Draenei. Creatures literally changed and shaped by their partial merging with these powers. That’s a new idea. Blood Elves took on the fel, High Elves Arcane, sure… but it wasn’t to this extent. It didn’t impact every one of their abilities. And the only magic fel-use seems to outright prohibit is shamanism, and even then not to the extent that green orcs couldn’t eventually reclaim it.
By introducing a race based around a cosmic power, like Light and Void, one of the key classes they need to be able to play is priest. Which, depending on your spec, focuses on Light, Void, or a bit of both.
Which means that in both cases you now have canonical examples of races using powers not only against their societal values, but oppositional to their very nature.
With that in mind, what’s to stop Forsaken Paladins? Gnome shamans? Tauren rogues (yeah, you heard me, stealth is against their nature, they BIG BOYS)
At this point, they might as well open the floodgates completely. Except maybe to hero classes. We probably don’t need dwarf evokers running around, breathing fire, burning their beards. If people can use powers opposite to their very nature in lore, then it doesn’t seem hard for them to learn these powers from other societies, in an increasingly multicultural and connected Azeroth.