Pretty much by definition its not going to be good at highly custom or uncommon programming tasks since it won’t have seen many examples to generalize from. I doubt you could get better results from a freshly hired human either.
But the human will learn, through reasoning and challenges... Those features of which some wonder whether they will emerge are critical pieces.
That depends on the human, what they're trying to learn, and how it's taught to them.
Some people with brain damage, learning disabilities, other cognitive issues, with poor teachers or learning materials, or with too difficult a task will not learn.
It might be useful to view AIs as akin in some ways to brain damaged humans, who might be good at some tasks but deficient at others.