A mind trained with the written word is different from a mind without it. The organization of thought required for reading is very different from that in an oral environment.
Literacy changes the way people think, or rather it opens up a new manner of thinking. It doesn’t necessarily supplant the discursive oral communication (elite Ancient Greek society, existing on the bleeding edge of the novel technology of writing, considered both oral and written language, in their proper uses, to be learned forms of culture). However, literate cultures have different qualities from illiterate ones.
Complex mathematics do not arise in oral cultures. This is not to say oral cultures cannot do math — you can find oral cultures comfortable with surprisingly high multiplication baked into their number systems. However, no purely oral culture has developed algebra or complex geometry.
Literacy is not just a communicative tool, although it is that too. Literacy causes a shift in how people think. It enables and enforces certain kinds of structured thought and is a step away from the gestalt, ad hoc compositional thought of discursive or oral communication.https://thesenecaeffect.blogspot.com/2021/11/the-age-of-illiteracy-what-is-exactly.html