Which I think could be done via the hypothetical questline I’m imagining if Blizzard isn’t a complete idiot and there’s someone on their lore team in charge of this that has the range:
I violently agree in that Undeath shouldn’t be cured, let alone via “The Light”, but the thing is Azeroth’s undead is achieved strictly via shadow, fel, light, and sometimes even arcane.
But that’s why Calia was a “Discipline Priest Champion” in Legion. That’s why she was raised with Shadow and Light and a Naaru that was a Void God just a year ago and is still strangely purple.
I think Calia can learn Necromancy from the Primus, real Necromancy, not the off-brand dollar-store version of the Lich King and the Nathrezim, and “perfect” the Undead by preventing their bodies from rotting anymore and learn magic that will allow the Forsaken to grow (still raising the dead) without the need of Valkyr.
Or develop in Shadowlands how if any Azerothian ends up in Maldraxxus, they have a chance to be Undead. More “ethical”.