I can honestly say, I was heavily influenced by the original Harn setting, that while fantasy based cleaves a lot closer to reality than many other socalled Euro-centric settings. That said, unlike D&D, much of medieval Europe's emphasis was the control of Europe by a single church (at least initially), though definitely a single deity. The fact that D&D settings use a pantheon of deities is a serious departure from the historic record. Pantheons of gods are pre-Christian and is more like an amalgamation of classical history shoe-horned into medieval history.
@Vidgange - yeah, I basically toss out all concepts touched upon during the Romanticism movement. My view of druidism, for example, coincides with Celtic beliefs/history, not with the Romanticism movement, nor modern alternative religious concepts of druidism. Druids of the past and socalled druids of today, have absolutely nothing to do with each other. Romanticism views on fey are nothing like the beliefs a century before or a thousand years before. I rely on Katherine Briggs views on fey lore, and not what Arthur Conan Doyle thought it was. Tiny tinkerbell fairies are a product of Romanticism, and not Elizabethan and older Celtic views on fey. At the same time the Color series of fairy books (ie: the Blue Book of Fairies) created during the late 19th century are actually fairly reliabe sources of fey lore. However, any topics touched upon in late 19th century, especially during the Victorian period/Romanticism Era, needs to be taken with a grain of salt, and very often should be eschewed as useless nonsense. It is better to research deeper, if you want to hope to better emulate reality or past beliefs. It is best to steer clear of any Romanticism notions.