He wasn't saying you aren't mediocre. He's just saying that often you don't see value in the things you already know how to do, because you assume others have the same problems and abilities that you do. Essentially he's just saying you need to step into your users' shoes better, it's not a feel good post.
I have the same problem, in that I tend to think that, if I can do it, that it must be trivial, when a lot of things that I can do at this point are not actually trivial for most people.
Still, I don't harbor the delusion that I could drop everything and write a $10k/month iPad app overnight. There's a lot of luck in that, and a lot of skills are required (marketing, presentation) that I wouldn't bet my career on me having.
I think it's worth it for people to try things that have a sub-50% chance of success if they'll learn something from it, and if they've limited their losses, but I think it's unreasonable to make major bets on not being in the N-1 out of N. The academic career racket is fueled by these sorts of unrealistic expectations (more specifically, by people who haven't figured out that the academic job market up-and-died a generation and a half ago).
