If I may defend Tolkien for a moment here, I wish to point out that his intention with The Lord of the Rings was to write a mythology for Britain like there was for Greece, Rome, and the Nordic countries. Mythological characters aren't supposed to be deep or very human. From the perspective of modern literature, all mythological characters are cardboard cutouts that follow archetypes because that was the point of these myths in the first place. In that regard, Tolkien deliberately limited himself (or maybe found a good excuse to work within his limitations as a writer?) and achieved his goal of making a myth.