Fiction is not meant to perfectly replicate the entire complexity of the real world - rather it takes a very particular subset of reality and distills into a story you can consume at your leisure. This is true for both fictional and non-fictional settings - no movie set during e.g. WW2 or the French Revolution actually conveys the whole complexity of the real world at the time. Can you imagine a version of LOTR that also had to convey the all the socio-economic intricacies of trade routes between Gondor and Brie? Do you think that movie would be more enjoyable, or better at telling the story it wanted to tell?
The best worldbuilding is that which doesn't get into the way of telling a good story. This is why "remixing" is actually a storytelling virtue - GRR can point at Dorne and vaguely motion "bizarro Moorish Spain" and the reader will instantly get a better idea of what he's dealing with without having to read a 800-pager on Dornish culture and history.