I'm about to start a Wow D&D5e game and one of my players showed interest at playing a Broken draenei. He and I both understood that the Broken wouldn't be able to wield the Light but then I started thinking about why.

At first I thought it was because the fel the orcs used against them had tainted their very being and the Light would not answer due to this, but then I remembered Lothraxion, a literal demon, was recruited by the Light and has now become one of its greatest champions, so I doubt it can be that. Then I thought it could be that the Broken are plagued with doubt about the Light, but as far as I can remember in Nobundo's short story he still fully believes the Light will come to his aid after his degeneration begins. So why exactly can't the Broken use the Light? If there is evidence of the undead, death knights, and demons using the Light, why can't the Broken do the same?