He's actually giving decent advice which is make yourself a source of knowledge on something within your chosen field.
Most people who are just starting out are not going to create the next amazing thing, but it's within reach for them to become a subject-matter-expert (or at least start that journey) so that they can use that knowledge to help them make things (and in the process support their peers and benefit from knowledge sharing).
I've wasted so much time in my life trying to learn things top down... that is, learn bits and pieces of something to complete a task without fundamental knowledge of the thing I'm working on. I've noticed "geniuses" never work this way. They insist on knowing their fundamentals first and work up from there.
A genius' mental framework for problem solving is so well developed that it just seems like they won DNA lottery. Carmack is incredible at what he does, but there are likely many intellectual things that he is terrible at because he has no mental framework for solving those types of problems. It ultimately would take him thousands of hours to be great at those things like the rest of us plebs.
To a large extent, career success is the result of a combination of hard work and luck. The more you have of one, the less you have to rely on the other.