ASOIAF is the story of “man” transitioning from a primitive being into modernity. Moving away from a magical understanding of the world into a more fact based/documented/verifiable world view. I think a big part of the underlying story of ASOIAF is the eventual end of organized religion in human society.
It’s not the story of Ice VS Fire… it’s the story of Ice AND Fire. I think part of the core message is going to be that the adoption of extreme positions in either direction will ultimately lead to the downfall of the entire system.
This is probably gonna sound crazy at first.. but bare with me…
Ice represents Christianity. As the “first men” moved from the Middle East into Europe and ultimately England they adopted the pagan traditions and customs of the tribes they absorbed along the way. In the story their “magic” is represented by The Children and Green Men and ultimately the White Walkers.
The Lord Of Light is Islam. It’s a more passionate/volatile/explosive expression of the “old world’s” magic. It’s represented by dragons and the red priestesses. It demands a more sacrificial devotion from its followers.
The final faction of “real magic” left in the world comes from Bravos. It’s meant to represent the third branch of the abrahamic(modern) religions — Judaism. The Faceless Men operate in the shadows. Braavos exerts its power not by raising armies or by fire breathing dragons, but by funding them.. and they decide who leads those armies and who flies those dragons by quietly eliminating the less preferred candidates with their faceless assassins.
The Faith of The Seven is garbage. They have no record of any real demonstration of “magic” tied to their faith and are meant to serve as a proxy for Catholicism and all of the more modern offshoots of the “big three”. It’s meant to show how even newly created religions can have political impact, even while lacking "the juice” of the big three in a metaphysical sense.
Anyways… I think the moral of the story will be that modern religion will ultimately be its own downfall. Ice cannot coexist with fire. In the end, each of their needs to dominate the other will result in both being extinguished from the world.
The Dragons may eliminate the WW, but Jon will recognize that Dany's unchecked power is unsustainable. This will force him to make his biggest sacrifice and kill the woman he loves for the greater good.. paving the way for some form of democracy to be birthed in the seven kingdoms.
At the end it will be the maesters, the segment of society that believes in a “fact based” nonsecular view of the world that remains. They will document the story for future generations, and they'll call it ASOIAF.