You are right that worldbuilding is his strongest attribute. His characters are getting better and better and Stormlight's are his best yet (imo). Keep in mind that he is still evolving and he is prolific. He generally releases 1+ books every year while still being a professor. Martin's books are really solid, when he ever writes them..... Remember this is his opus after a lifetime of writing. (I personally think his Fevre Dream is a great book)