Agreed that societies can get sophisticated without writing, but Egypt was already considered mind-blowingly old in Plato's time.
The start of the Timaeus features an eight thousand year old Egyptian city with an eight thousand year long memory. It also says that Athens is even older, but that it's periodically destroyed by natural disasters, losing its history and technology. Writing is mentioned as one of the things lost:
> Whereas just when you and other nations are beginning to be provided with letters and the other requisites of civilized life, after the usual interval, the stream from heaven, like a pestilence, comes pouring down, and leaves only those of you who are destitute of letters and education; and so you have to begin all over again like children, and know nothing of what happened in ancient times, either among us or among yourselves.
Egyptian hieroglyphics were already thousands of years old at the time! I think the myth in the Phaidros was meant to be understood as taking place in a mind-blowingly past aeon.
The start of the Timaeus features an eight thousand year old Egyptian city with an eight thousand year long memory. It also says that Athens is even older, but that it's periodically destroyed by natural disasters, losing its history and technology. Writing is mentioned as one of the things lost:
> Whereas just when you and other nations are beginning to be provided with letters and the other requisites of civilized life, after the usual interval, the stream from heaven, like a pestilence, comes pouring down, and leaves only those of you who are destitute of letters and education; and so you have to begin all over again like children, and know nothing of what happened in ancient times, either among us or among yourselves.
Egyptian hieroglyphics were already thousands of years old at the time! I think the myth in the Phaidros was meant to be understood as taking place in a mind-blowingly past aeon.