Well, as much as I admire EW, I think he may be off on this one.
I go to the musician analogy.
A beginner at the guitar can never appreciate all the qualities - both visual and tonal - of a $4000 Martin CEO-8-2e, but it will be far easier for the beginner to play than the $50 Walmart special because it is precisely tunable and the action is quite easy. I am not suggesting that every beginner get $4000 guitar, but no beginner should start out with the $50 one either. There is a middle ground on price for ownership, and usually a low cost rental option that works as well. When the skill level increases, so should the quality of the instrument.
Photography gear is no different. Usually people start out with a modest camera and lens(es) and work their way up. As you improve your skills, or develop specific interests in subject matter, the original purchase may not suit their needs. It has nothing to do with mastery - but all to do with focus (pun intended). One does not need to have a full, in-depth understanding of a camera and a kit lens to know that they won't get amazing results when shooting high school football in a dimly lit stadium, or indoors at a birthday party with a combination of light - including the pop-up flash. So they start their quest for better results. Of course there is technique that needs to be addressed, but even with good technique, an inadequate camera can be an obstacle to getting quality images.
The other important component is the marketplace. Every year brings new gear. Digital cameras have been on a very fast R&D cycle, with improvements in sensor technology (higher res, less noise, better color), handing (faster processors, bigger buffers, ergonomics, etc), size, etc. The R&D on lenses is a little slower, but in many cases, the new stuff is discernibly better than the old stuff. Or cheaper. Or lighter. Or more resistant to poor environmental conditions. This constant advance of technology, coupled with the advancement of skill level and creative desires, is often what leads to GAS.
Of course, there is the other very human part - it's exciting to get new toys! And many people who get the new toys or gadgets often figure out how to best used them. I have yet to know of any working photographer that shoots in the field and/or studio and doesn't have a small warehouse of "stuff" for the job.
The other thing is that "stuff" breaks and routinely needs to be either repaired or replaced. An excellent opportunity to replace with newer, better gear. GAS has it's place and there is nothing wrong with it. And you don't have to master what you have to "merit" something new and better. You just have to be able to afford it.
Well, as much as I admire EW, I think he may be of... (