The light was never a force of good, but of faith.
I see many people saying how the lore in midnight is trash, how they distorted the light, but i disagree.
The light was never a force of good. We saw it in warcraft 3 when arthas still managed to use the light even after killing lots of innocents in stratholme.
The light follows faith, it's always been that way. The " paladins blinded by the light" we see in midnight, like in the raid? It's just the typical zealot, like the scarlet crusade.
We never focused in the scarlet crusade so much to notice them turning into crazy zealots, but in midnight, we live with them, we interact with them, so we see it happening first hand. Lothraxion already looked like a zealot in legion, but his focus was in the burning legion.
No matter how evil someone is, the light help anyone with enough faith. That's why anduin didn't use the light for some time, because he lost faith after what he did in shadowlands