I came at it from a different angle in my 2012 blog entry on the Top 5 Prospect Interview mistakes. Your point about hypotheticals and predicting the future is well taken and, I believe, the most pervasive mistake product managers and user researchers make when interviewing prospects.
As for “no new jobs” and “problems that aren’t being solved yet”, I think your treatment fails to distinguish between a job and an unsolved problem.
In the jobs-to-done framework, a job doesn’t always correspond to a problem. Problems occur in the context of a person trying to complete a job.
It is true that there are no new jobs to be done, or at least that new jobs arise only rarely, and as a result of disruptive innovations.
But there are many unsolved problems (“unmet needs”, in JTBD lingo) that occur within the context of a person trying to execute a job. It takes too long. It’s tedious or emotionally painful. It’s expensive. Sure, users are already executing jobs, with or without our solution. But there are plentiful opportunities to solve problems they are facing, and our primary task when interviewing prospects is to identify those unsolved problems.