Literacy is actually not a requirement to vote in Canada. If a person is not able to read, due to blindness or not being literate in English or French, that person is allowed to have someone to read the ballot and instructions to him/her. The helper is required to take the Oath of Friend of Incapacitated Elector, which is basically a promise to mark the ballot as the incapacitated (for this purpose, an illiterate person would be considered "incapacitated") elector directs. Both of them go to an empty station where the elector tells the helper how to mark the ballot. Of course there's no way to verify whether the helper actually does this or uses it as a sneaky way to vote for someone else, but the fact remains that illiteracy or other reason for not being able to read the ballot is not a valid reason to deny a citizen their right to vote.
Illiteracy doesn't prevent a person from watching TV, listening to the radio, or talking to people. Of course they don't get as much information as a literate person does, but they're not completely out of the loop.