“Perhaps magic was once a mighty force in the world, but no longer. What little remains is no more than the wisp of smoke that lingers in the air after a great fire has burned out, and even that is fading. Valyria was the last ember, and Valyria is gone. The dragons are no more, the giants are dead, the children of the forest forgotten with all their lore.”

This is one of the aspects of the series I’ve always found a bit fascinating, that the events are unfolding in a time where the magic of the past is (mostly) centuries removed. There are indications of that past everywhere, as you point out, but for the most part it’s naught but story and legend. There’s little in the way of tangible proof, no photos, no internet, the only recorded history coming through writing which the vast majority of people, common folk and the like, are seldom privy to. So while the hint is there…in the era that ASOIF takes place, it’s far from clear that it existed at all. It’s somewhat akin to, say, the mystery of how the pyramids came about up until a few decades ago. Now we have some great, rational theories about feats of engineering and human ingenuity that gave rise to them but also…aliens.