I think this is a negative story.
Its disastrous implication is that "not gifted students" should never opt for a career track, because perhaps they can be Gedolim, just like the Netziv.
It is the most anti-TIDE story I know, but even more so, enough to impose an eternal guilt trip on so many people who would actually do well to seek a profession and be neheneh me'yegi'a kapeihem.
From: Boruch Horowitz
Quoting Dr. Levine,
"He came out of his room and said to me, "Abba. Finally someone who is
human." I asked him what he meant. He replied, "In this book it says that
the Netziv was not a gifted student, and, when he was a teenager, his
parents considered taking him out of yeshiva and having him taught a trade.
All of the other books talk about people who are geniuses and perfect. Here
is someone who is real!"
That was my reaction to "My Uncle the Netziv" as well. I think the
informal, first person, style also contributes to the sense of reality. R.
Baruch Epstein certainly comes across as human, himself, in his memoirs.