I was 30 years old when I learned how to think for myself

I learned early in my tech career, how some people look at things with a set of data, is why many experts make broad claims. I've seen too many things that don't match in prod/life that works as documented/expected. Once you see this enough, you start to think for yourself on why.

Also expanding your cognitive skills with communication and maybe debate skills, you start removing the blinders to single points of view, and you start seeing new alternatives/possibilities.

Lastly, believing you have to have/be the best for a feature/taste, and not saving money for "good enough", opens up looking into alternatives, and increases thinking for yourself. Not having to be a follower or accept peer pressure.

Oh, and as for projects, sometimes there's goals/drivers you don't know, knowing those drivers helps expand your thought processes.

All this relates to life outside of work too.

I'm happy for the author, they're growing. The article is basically how they transitioned from passively accepting external truths and making internal judgements to developing their own internal discernment. This shift has transformed how they view the world, tested ideas, and understood people. A technical person "seeing the light" of social interactions and the usefulness of soft-skills in life.