You mentioned that GRRM is weaker on the sociological aspects of Medieval times. Does this include the severe neglect/abuse of the lower classes? It works well to explore his theme of 'True Knighthood' and existential heroism in the books, but what could a real peasant count on his lord to actually do for them during siege or chevauchee? (Even if only in a self-interested sense of 'I need X peasants alive to work my fields and tax myself into splendor.')
As we might expect from a writer of his generation, GRRM does better with class than he does with race or gender or sexuality. He's still imperfect - one major non-noble POV in a book made up largely of noble POVs isn't exactly representative - but you do see his depiction of class inequality through the impact of the War of Five Kings on the Riverlands, the Broken Man speech about the War of Ninepenny Kings, the King's Landing riot and the Sparrow movement, etc.
At the same time, while GRRM certainly knows what town and city and guild charters are, he doesn't really show the burgher class as an active force in Westerosi politics (outside of the Antler Men) the way they should be given the degree of urbanization that's supposed to exist.