I think doing 'what you love' is a failed premise for several reasons.
a>When you turn your passion into a job your passion becomes a job.
b>You only 'think' you love it. Your social circles have conditioned you to love a certain subject. An inner city kid is going to be more likely interested in the NBA and Rapping, than social media and solar power. Just like the average person from the middle east will be more interested in Islam than the average person from the South. (Stereotypes can be proven by statistics.)
c>You will change. As you get older think of all the new things you've fallen in love with. New passions. New interests. And the things you have fallen out of love with. I'm not convinced people are static enough to love 'one thing' for 40 years.
I think what people really want out of a career is freedom. Intellectual freedom, freedom to manage their time,prestige, respect, expertise, etc.
I think these are the things one should be pursuing instead of doing 'what you love'.