The small number of passions that most people can't earn enough from to maintain their existences tend to be those which are (i) shared by a lot of people and (ii) those in which success is least easily achieved through sheer willpower. Want to be an actor, a sport star, an author, like many people do? Chances are you'll never be good enough to earn a living at it (unless you count being a salesperson, personal trainer or author of press releases) because everybody else practises, and some of them are better and/or luckier. You can still have that self-actualization with your spare time drama group, sports team or novel that's just waiting for the right publisher, but in the mean time you'll probably need to spend the majority of your waking hours chasing an alternative source of money to put food on the table (sacrificing passion is very rarely about getting rich quick). It probably won't be in finance, because finance firms have exceptionally high standards too and you'd be surprised how many people are passionate about it. Want to be a bookkeeper or a refuse collector? No, neither do I, but someone has to do it and it's probably not their lifelong career aspiration.

I agree with your general point that focusing your attention on what earns the most money is likely to be a recipe for dissatisfaction, unless money offers you everything you want. But the article seems to be making - somewhat fluffily - the perfectly reasonable point that successfully solving others' problems barely related to your interests will usually satisfy (and earn) more than consistently failing to interest the world in personal projects the market doesn't care for, especially if that's because you simply don't have the aptitude to complete the project.