As far as I know, the term "demotivational poster" originates with
Despair.com, which produces posters that make an extremely cynical comment entirely at odds with typical motivational posters, supposedly intended to de-motivate a person.
Posters like these, which are simply absurdist, and make no real satirical commentary, can't really be called "demotivational" except in the sense that they are at least partially inspired by those posters produced by Despair.com.
Also, someone truly illiterate wouldn't put the apostrophe at the end of a word like "doin" in place of "g"; doing so indicates active knowledge of the misspelling.