what are the contributions of writing in getting knowledge?

Writing has never contributed anything in the getting of knowledge.
Writers have often given adivice though.
One piece of advice that great thinkers have always given, we learn by experience--not by hearsay.

not everything is a philosophical treatise, just in case you didn't know that

the poster might be asking about the advent of writing in disseminating knowledge or information

But there is always a chance that the poster understood the reply, whereas it is obvious you did not.