The worst part is that both lightforged and void elves have a ton of potential for insteresting stories. The lightforged have this history of battle and war, of having no place to call home, of following rigid military order, of zealotry. All those can be interesting when clashing with civilian life, living in Azeroth, different faiths? They are also supposedly badass soldiers, an elite force that faced the Legion for millenia. Yet, there's nothing exploring them so far.
THe void elves lack even the most basic depth. Who are they? Why they chose to study the void? How they create more of themselves? How are they adapting to the Alliance? What's their ethos? What trials a potential void elf face in order to be transformed? What elves seek them? Nothing, just nothing.
They have nothing but potential.
When you create a new highmountain or nightborne, and see their intro narration, it calls back to all the experiences we had with them in Legion. When you create a new void elf or lightforged, you feel like their entire lore is described in the intro narration. It doesn't summon any great memories from the player.