I also studied art, but history as well.
If you look at things like Greek sculpture, and even some ancient paintings/frescos, it's clear that they understood perspective and anatomy perfectly fine. But representing photorealistic scenes wasn't what they were after, particularly in medieval times. Paintings were about symbolism and conveying a message to illiterate populations rather than beauty, so the emphasis was being as clear as possible, often at a distance.
Consider it like an artistic choice rather than a limitation. Of course, there's always less than stellar artists occupying the scene as well. Sculpture was considered to be the higher art with more permanence, so if you were really good, you likely didn't paint/draw much. The Bayeaux tapestry wasn't made by artists, but rather noblewomen for instance.