That is a fictional objection raised by the Egyptian god Amun to the Egyptian god Thoth, who was supposed by the Egyptians to have invented music and writing, and was supposed by the Greeks to have invented absolutely everything else too, including botany, surveying, and government.

It's also a critique of writing, written by Plato, to impress on us that Socrates was great orator (or arguer) and was better that way. But it's not somebody's reaction to the invention of writing. It's an imagined reaction to the invention of writing.