I will say this as I have said a million times before:
All equipment has limitations, even the most expensive. A good photographer can make great images within the boundaries of these limitations. While a high end setup is going to have fewer limitations than a cheap point and shoot, it is up to the photographer to understand the limitations of his or her gear - thus likewise, a camera with more limitations will be much more challenging to use to create compelling images than a less limited kit.
Also, as I have said before, this thread is not if primes or zooms are "better", "sharper", or "more convenient", but rather if primes help promote photographic skill. So what is better to improve with? If it takes a good photographer to make compelling images with more limited gear, wouldn't it make sense that you'll learn more with the more limiting option than with the less limiting option?
It has been demonstrated that a photographer who is proficient using a set of primes is also proficient using a zoom; however, I think that the learning curve in the other direction is much steeper, and I have to wonder how frustrated some of you would be if you were forced to shoot only with a normal lens - not because using only a single focal length is impossible, in fact many great photographers throughout history relied only on a set number of focal lengths, if not only one, but rather because composition considerations are entirely unique when you don't have a zoom to rely on.
Even the phrase "zoom lens" is misleading, implying that the only reason to use a longer focal length is to get in closer to subjects which are too far away, and perhaps more commonly, too lazy to approach, and I am curious how many zoom advocates really think about focal length in terms of space, DOF before they think about magnification.
So yes. I think that primes do help people become proficient. They allow us to slow down, think about not only the subject and composition, but also photography. Primes are more limiting, they are less convenient - and that is exactly why they good.