"Advanced for their time" is a misleading thing to say. I don't mean to call you out on it, but you have the unfortunate pleasure of being used as an example.
There's a misperception that as mankind moves toward the future, we are necessarily improving in general, as if something in our nature guarantees progress. We consider ourselves more advanced than the generations that have come before us by virtue of having had more time to learn and grow.
The problem is that that assumption relies on the idea that we have always been constantly working towards the same goals and that those goals will result in our advancement, however you may define advancement.
Even if the assumption that our progress as a species is directly proportional and correlated to the time we have existed is correct (whew, pause for breath), we've still encountered serious setbacks on the road to that progress. Not to abuse already overworked historical tropes, but think of the European "Dark Ages" and the burning of the Library of Alexandria. We know that tremendous amounts of literature, scientific knowledge, and recorded history were forever lost in cataclysms of war, plague, and migration. Who can say for sure whether ancient peoples were more or less advanced than we consider ourselves? The Romans didn't even have a concept of zero or knowledge of calculus, and they considered the principles of the steam engine as good for toys and nothing else, yet they were the dominant force in engineering in the Western world and achieved feats of architecture that subsequent cultures weren't able to duplicate for centuries.
What I'm getting at is that to say a culture was "advanced for its time" betrays a mode of thought that assumes our current notion of advancement and our current priorities of knowledge and the application of knowledge are correct. That's a dangerous road to go down, because it can lead to an arrogance of perspective that limits our ability to appreciate the accomplishments of those who have come before us and to see the real value in the past.
