There are other jobs like this: Surgeons, airline pilots, and tympanists. Maybe the skilled trades in general. Sure, the good ones may show their brilliance on rare occasions, but those don't happen often enough to show up in a statistical study. Mainly they need the training, practice, and self discipline to follow the correct procedures and get it right every time.
I'm thinking of an analogy, which virtually guarantees that it will be a bad one: A bad plumber would be bad for the performance of my house, but a good plumber can't really make my house perform any better. Yet I don't want plumbing to be run democratically in my house without a plumber. (Note: I'm the plumber in my house).
Perhaps the "good" part of being a good plumber is doing the job correctly every single time and not making mistakes. If this were the case then I'd argue you are a perfect plumber. At what point on the scale does a mistake or mistakes take you from good to bad? A plumber with a 90% success rate is, in my definition, a good plumber as the stakes are not as high. A surgeon or airline pilot, in my mind, must have a 100% success rate in order to be considered competent since lives are at stake. You'd be hard pressed to show that a former CEO that now has a different position at another company is not a CEO due to being a bad CEO as they likely wouldn't be hired at all for any high-level position.
To wrap this up, if there was still a plumber out there that was a bad plumber then I suspect he/she wouldn't be a plumber long enough to still get jobs.
A good plumber can make your house run better if they come up with a more efficient or innovative way of doing a process that you didn't think about but in your mind that wouldn't make them a good plumber but merely a plumber that follows processes and doesn't make mistakes. If not for mistakes then we may never find better ways of doing something.
It's structurally made virtually impossible to do such a thing. Nonetheless, this approach was successfully applied in Argentina. There's a good documentary about it http://www.thetake.org/
http://www.fastcompany.com/27333/trillion-dollar-vision-dee-...
And in case anyone wants to discuss chaords:
http://www.theguardian.com/business/2012/jan/16/john-lewis-m...
That said, they do have a Chairman who is basically a CEO; he answers to the employees rather than shareholders, but i'm not sure how much that changes things.
And of course there's the Co-op, which is a patchwork of regional and national organisations under a common brand which between them provide a range of services so wide they're virtually a shadow state:
I have no idea how they are actually run.