I don't think it's too unreasonable to assume more modern people (significantly more modern, even), are a bit more enlightened on some subjects. At least, we no longer consider things like slavery and sexism OK, yet ancient people did, which indicates some significant gaps in their philosophies and high influence from outside.
> Have you considered that this "primitive" idea comes up over and over again among great thinkers and writers throughout human history because there's something to it?
Well, there is something to it... it's often reflecting the natural order of things, or the Zeitgeist of that time. Generally, a great thinker does not transcend time and is somewhat locked into their time, in that only certain strains of thought seem to exist during a time period and others do not, which indicates that overall variety of thinking is just not very high, regardless of how much of a "great thinker" you are.
This, of course, it true for our time as well. Very likely many things we believe today are heavily influenced by whatever is, in a sense, "fashionable". Some ideas are best left unstated.
The age, or lack of thereof, won't really tell you how accurate or useful something is, you'll have to evaluate it on its own terms. I don't like terms like "primitive" because they don't mean anything on their own, but that's a different question.