To be fair, Aragorn was also in a low-magic setting barely comparable to baseline D&D. Magic is extremely common in D&D these days. The modern guidelines are something like, 20% of a population are more than commoners, martials are twice as common as partial casters, partial casters are twice as common as full casters, and there's half as many people at each level as there were at the level before it. The math works out to be something like 6% of the population being fullcasters of various types. Out of 100,000 people, a large but plausible size for a medieval city, 3,000 of them have 1st-level spells, 750 have 2nd level spells, 186 have 3rd level spells, 48 have 4th level spells, and even 12 have 5th level spells... A far cry from LotR's "there are five wizards in the world". A 13th-level spellcaster is something like 1-in-200,000, rather rare but not unfathomably so.