And in case you were thinking, rewriting from scratch is not sufficient to transform a big ball of mud into a greenfield.
In any case, the opportunities for refactoring big balls of mud are growing exponentially so it is a worthwhile skill to master.
What I do know is that I have been the 10x guy up until my latest thing, where finally, thankfully, I'm surrounded by people who are on average better than me.
10x, though it sounds objective, is a very fluid term. What I've noticed is that everyone who plays at this level cares deeply about code quality. It's about art meeting functionality, and all of that being shipped on time. It's about avoiding technical debt, except in rare cases of grudging agreement in the face of cold hard facts.
10x is discipline and drive. It's not that they choose to, it's that they're DRIVEN to.
I agree that this is a challenge for management. Writing good computer programs for 40+ hours a week is an unusual thing for a human being to do. Doing it at 10x over the long term is just plain unnatural.
Individuals seem to require their own (evolving) set of motivations and circumstances, making successes very challenging to replicate.
I call myself a 121 programmer, which is the MacLeod Sociopath of the programmer world. (911 are MacLeod Clueless because they're willing to throw down in an emergency that management created; 501 developers, who leave at 5:01, are MacLeod Losers.) I want to improve the value of my skill set by 1% every 21 days.
There is 10x of selectivity (choosing good projects) and also 10x of productivity (making good calls) with the latter especially prominent in powerful languages (e.g. Lisp). But "10x" doesn't happen overnight. It happens over a long time. Taking the 1%/21-days estimate (which is a wild guess, but the right binary order of magnitude) that means we go from 1x to 10x in 13.3 years (although I've actually seen people grow faster than that.)
The 10x programmers got that way by mandating that they learn, and ignoring career-incoherent work.