The noble and cleric can't read? Classes that effectively have to read in 5e and similar systems:

Bard: plays, music, stories Cleric: holy texts Monk: holy texts if they are the monastery type of monks Paladin: if trained w/clerics or in a temple. not if they are wild-sprouted paladins. Rogue: thieves' cant, smugglers for manifests, forgery. really just the average cutpurse and enforcer wouldn't need to Wizard: a nerd's nerd

Artificer: inventor's notes.

That's why we keep the low level wizard around

Then deliver quests via talking owl, like in Zelda