I was like this for a while, working in restaurants and the sort before going back to school, and in these jobs you find a lot of people who are afraid to place a bet on a career so they can focus on some wholly non-unique set of "interests". I noticed that few of these people actually pursue these supposed passions to any real extent, and most of these interests were strictly of the creative, non-pragmatic category.
I figured that such jobs offered flexibility from the rigid 9-5, and would allow one to pursue these "interests" more freely. This is not the case. Working a developer job you have mental stimulation from learning new things and getting things done. This is normalized of course, and so it's important to remind that working odd jobs while you "write your novel" is entirely devoid of such stimulation, and I believe, actually and actively kills brain cells. And this is the path the author suggests many of our "undecided" college graduates will go? Say it ain't so! If you want to write a novel or learn to paint, and if these are genuine passions, you will make time after work and on the weekends.
It's less about "finding your passion" than it is developing a discipline to work on big projects that is completely absent from high school and non-STEM college education. Take your average "undecided" and finance them for a year to follow their passion. A few will make something of their time. Harper Lee did, writing To Kill a Mockingbird uninterrupted for a year thanks to donations from friends. But most will not for the same reason many of us developers (mundane corporate drones) struggle with our own interests and side projects--- because we all lack the discipline. Bukowski summarizes this "myth of creativity" well: http://www.brainpickings.org/index.php/2013/10/04/charles-bu...
It feels good to solve hard problems and challenge yourself. Doing so at work acts as a momentum towards your other goals and interests, and with persistence, lead to a discipline of continued creativity.
In case you have not read PG's high school graduation talk, I highly recommend it. Very relevant: http://paulgraham.com/hs.html