I always thought the typical D&D adventure setting was more akin to the Wild West with trappings of the middle ages. There is typically far more sexual and racial equality than there would be historically, the idea of an entire social class of semi-itinerant people carrying the heaviest weapons they can carry on their persons for self defense, seeking fortune and fame, and tending to go off like vigilantes (or at best an ad-hoc quickly deputized representative of local authorities) to bring justice to an evildoer is more suited to Zane Grey than Chaucer.
It is actually mostly disguised Victorian & Wild West culture, trappings and technology of the early renaissance, and some "cool" elements from antiquity and the middle ages dragged along.