A word to describe somebody with smartphone-only tech skills
Solution 1:
A person who knows how to use a fancy state-of-the-art app with great ease and familiarity is just a competent "user", they are not a developer or programmer.
A user (computing) is a person who uses a computer or network service. Users generally use a system or a software product without the technical expertise required to fully understand it. (Wikipedia)
I might refer to this person as a "non-nerd" but I admit I don't know if this was a commonly-used expression, it makes sense though.