The theme of good vs evil predates Christianity by a lot. Furthermore, the theme of good vs evil in Warcraft is extremely different. It’s never been in World of Warcraft. Not ever. Look at the classic races, and their diverse religions, lifestyles, cultures, etc. Look at how the Light isn’t a god, and even as early as BC (where the Naaru are introduced), e.g M’uru. It has always had this theme of “morally grey,” which has itself become a caricature over such a long span of time.
But let’s return to Queteron’s original post. It offers no substance, whatsoever. It makes claims without backing them up. Then again, I suppose that is how scripture works. No evidence means it should just be thrown aside. It is a fantasy to believe that Warcraft lore has a “Christian foundation.” There is a reason we don’t see stonings in Stormwind, or carpenters nailed to sticks, or such. It is a romanticisation of fantasy religion, far more akin to D&D than anything else. He also seems to claim the West is based on Christianity, which is demonstrably untrue. It was the rejection of this through the French Revolution that has set up Western culture. Furthermore, he just seems to claim buzzwords as being only applicable to one religion. Similarly, claims that topics of “literature, religion and humanism are gone,” is also just incorrect. The only thing that really deserves pointing out is, " Back then the story was centred on the great struggle between life and death, light and darkness, hope and despair, with knights, crusaders and priests fighting under the banner of the good and true against the forces of evil. That was Warcraft at its peak!"
And that simplification doesn’t even cover the vast array of nuances, but it is the closest thing to truth offered in the post. Not to mention it involves ignoring the vast majority of the expansion to accept that worldview. I find it difficult to accept that people can merely voice support for something without basis, without evidence.
But back to your post, now the OP is out of the way, I want to address some of your narrative points.
In the same expansion they were introduced, we knew they could turn evil by ‘dying.’ And on the same topic of the Light, we know that can be harnessed by anyone for power. The Light is no god, nor are the Naaru. They are simply beings of it, and have always just been doing their own things in-game.
I’d suggest that this has always been the case. There’s a reason why classes can use shadow, undead, and fel abilities. It’s never been a case of black/white morality here.
In Shadowlands, I’m pretty sure we still see reference to people dying, and just staying dead. No loitering in the Shadowlands. On the contrary, I find things far more nuanced for when we’re out of the Shadowlands. When somebody dies, they don’t just simply go to an afterlife - they just all go to suffer in the Maw. As far as interesting moral dynamics go, we’ve not had better since Elisande in Legion.
I think describing the Warcraft cosmos as “cold and nihilistic” to really be just an expression of its afterlife not being one you believe in. Probably because there are multiple, and same with gods. Would you consider Elune, the Loa, the Earthmother, the druid demigods, etc. to offer this same notion of being cold and nihilistic? No, it offers the contrary. There are a vast array of characters in the lore, and they all enjoy their own afterlives catered to their religious groups. It’s precisely the opposite as cold and nihilistic.