Probably differs a lot, but the Navajo have a massively developed story-telling tradition to pass on wisdom across generations. Iirc these are symbolic and has moral or philosophical contents, similar perhaps to fables and religious miracle-stories. Encoding information in narratives is highly effective for memorization, and I believe deliberate so. Literal interpretations can be fun, but a deeper semantic interpretation can really unlock ancient wisdom. It's fascinating.
Even if remembered perfectly and consisting only of valuable information, it's amount of knowlege that fits in a single brain. We are centuries past the point when such amount was significant.
You could distribute specialized knowledge among different people, so it's not as restrictive as a single brain. And to be fair, our most valuable knowledge today is probably encoded in few people's brain as well in the form of institutional knowledge. But I get your sentiment, writing down is an immense construction that expands the topology of knowledge by a huge factor.
