"which suggests they have no real desire towards"
How could someone have desire towards something they have never tried? I never realized programming was the most exciting thing a human can do before I had my programming 101 at university and 14 years later I'm happily employed as a software engineer and fairly competent at what I do.
" If I'd never baked a thing in my life and said "I want to go to catering college" I'd pretty much expect teachers to say "Really?"; why is this different?"
I would think the person would find out soon enough if it works for them or not. Most precious things in human life are often the result of serendipity.
What is a good occupation? I would say it is a one where the basic value adding functionality is enjoyable to a person and brings them energy. A bad occupation is one the person hates. If someone has never done something, but find out after trying that they really enjoy it, I would say the odds are that he or she might become pretty good at it since they enjoy it and they have extra mental energy to spend.
Decisions made based on intuition cannot be logically baked without lots of hard work. Sometimes it's impossible. However, evidence based, empirical proof is easy to gather. If someone does not know would they like something, they should try it.
It's far more efficient to try it first and if it does not stick, then try something new. I would claim it's quite impossible to figure out before hand if someone would like doing a thing just from applying basic logic.
I would say the agile ideas are pretty good for personal life as well. Try new things, see what happens, but do not become victim of the sunk cost fallacy - fail fast and all that.