thumblefingered

A person so unfamiliar w/ new technology that they are unable to type accurately on a smartphone or tablet using a 2 thumbed technique
Being so clumsy that you are unable to type accurately on a smartphone or tablet using a 2 thumbed technique

That thumblefinger can't manage to text me a message that makes any sense.
I'm so thumblefingered that it takes minutes to two a Google search or send a text