Douthat hints at a larger point for which Tolkien has been criticized: an alleged oversimplification of evil. In LOTR, no ambiguity or drama exists in the determination of who is good and bad in Middle-earth; we never learn exactly why Sauron is evil, nor exactly what he did to earn the status of chief antagonist. The intrinsic nature of Sauron’s evil may even strike modern sensibilities as mildly unjust or at least arbitrary. Fantasy writer Michael Moorcock mused that as readers “we are not sure . . . if Sauron and Co. are quite as evil as we’re told.” This is because, as another author, Fritz Leiber, put it, Tolkien “does not explore and even seems uninterested in exploring the mentality and consciousness and inner life of his chief villains.”

Bradley Birzer observes in his wonderful book, Sanctifying Myth, that Tolkien refrained from probing the depths of his evil characters by design—since the reality and, indeed, the banality of evil does not require elaborate fictionalization:

The monsters of fiction and nightmares are merely manifestations of the true, original evil—the perversion and mocking of God’s creation. In its essence, evil is and always will be merely derivative and perverse.

Rather than contriving Sauron’s particular evil actions, Tolkien portrays evil as a force, one that is “outright ominous, for it seems to be everywhere, pervading the entire landscape of Middle-earth, surrounding the Fellowship of the Ring on all sides.”
— Read on www.thegospelcoalition.org/article/contrasting-views-evil-game-thrones-lord-rings/