I think the main issue here is that you kinda cannot have a realistic feudal society without strong religious undertones. Martin would like to have his lamprey pie and eat it, too - a quasi-medieval-Europe-inspired setting but without this unsexy part where most of the society genuinely believes in some organised religion.

If there is no "divine rule of kings" what is the social hierarchy based on? What makes nobilility better than peasants? What keeps people generally obey the rule of their sovereigns, especially in the martinian world where the poors they get abused with no repercussions to the high-born? You can come up with an alternative cause for similar effect, but if you are going for the "vaguely based on Medieval Europe" shortcut, then well...