In IT jargon we sometime use lamer.
A lamer is widely understood to be the antithesis of a hacker. While a hacker strives to understand the mechanisms behind what he or she uses, even when such extended knowledge would have no practical value, a lamer only cares to learn the bare minimum necessary to operate the device in the way originally intended.
ADDED after the OP had added a limiting condition:
I'm not looking for insulting or pejorative terms.
I guess you will hardly find any single-word term (in general, not only in connection with the computer literacy) with a meaning "lack of something", especially "lack of knowledge", with non-negative connotation.