As an example McDonalds "upgraded" their order taking turrets from using words for each food item to pictures for each food item.
Actually, chaning from words to pictograms speeds up the order taking process regardless of literacy level. Even an extremely literate person will be faster to recognise common pictures and symbols over words. This is why a lot of hazard warnings (chemical, flammable, corrosive, nuclear, biohazard) have a large symbol and smaller writing. The symbol lets you know it's flammable from a distance, the writing gives an educated observer some idea as to what or why.
That meant they could employ people who couldn't read, because I guess literacy was a limiting requirement in their hiring process.
This indicates a problem with your nation, not the hiring or order taking process.
In a lot of first world nations, applications to work in McDonalds requires a written application and in some cases, a simple written examination in the native language of the country (so a French Micky D's worker is expected to be able to read and write in French). Hell even in many third world nations like Thailand or the Phillipines literacy levels are high in fast food restaurants as you need a certificate in hospitality to work there.
Your thinking is obviously US centric. The US is the odd man out in first world nations in this regard as it tolerates a relatively high level of native language illiteracy and almost promotes a large underclass of non-native language speakers. Or in other words, education is inconsistent and there are jobs "Americans wont do".