I imagine within the tech world there are tasks that are ill defined and a small subset of engineers can solve, but a typical engineer may not have the background to solve it.
You actually hit this nail quite on the head with the example. The "10x engineers" get a lot of their "10x"-ness from creativity - most I've met are cartoonists, painters, musicians, writers, cooks - artists in general that love software as a way of expressing themselves and earning good money. The beautiful bits of code you get after are usually there because the starting point is "create it" not "implement existing solution/pattern".
I used to do design/graphix/ux work... that always interested me. Programming pays better, and I have a talent for it. I have spent time learning patterns, etc, but not through a formal education. I tend to just see a good way forward... creating discoverable code along the way. I find a lot of the time, the formal patterns tend to just make things more complicated than they need to be.
Just my own take on things. I'm kind of lazy in a good way. I have spurts where I will do a crazy amount in a short time, and those where I'm closer to coasting. Like many/most creative types, it varies.
The math is not that simple. The output of a Junior engineer is much different from that of a Senior engineer. You can hire any number of Junior engineers you want, and they won't have the vision and seasoned experience of a Senior engineer for producing higher quality code with less technical debt.
Even among Senior engineers there are different grades of experience/competence/capability.
central theme is that "adding manpower to a late software project makes it later."
Some engineers are just slow. I don't think it's much correlated with experience. If your goal was never to be a super productive programmer, I don't think you'll ever become one.
This might also be why there is this spectre of agism in the industry. Everyone knows there's greybeards out there that would eat your lunch and get paid the big bucks, but at the same time older programmers have hard times interviewing. At that age most of the really great programmers have probably already been fished out of the pond.
I will say, my recent stint of interviews over the past 6 weeks or so has been pretty painful. Everyone seems to be going through 6+ interview stages. The reality, even then, I'm not sure they're getting a great signal:noise outcome. Some of the tests are for things that will never be used for those jobs on any given day.
I do miss my 20's when an interview was maybe an hour and a half on an afternoon, and an offer shortly after.
They often seem to have the idea that it's more or less grunt work. Yeah, if a truck will haul 10 tonnes in one go, you'll get the same time if you hire an army of people, each carrying 10 kg on their backs, give or take economies of scale.
Another consideration is how much time we can afford for the solution to be wrong and need to be tweaked. For anything that has to work the first time, you want one (two, really) of your more sober and likely expensive engineers on the case, even if they aren't your fastest.
You may or may be able to replace your 10x engineer for this kind of work, but you're likely to be hamstrung by your interview processes.
But some things i think you won't be able to replace --
You won't be able to replace speed on short-term projects. Lots of people means lots of communication overhead, which really kills fast responsive speed. If you value time to answer, you'd prefer a small team of really smart people instead of a large team of average people.
You won't be able to replace the insights. Tasks and knowledge are distributed amongst many individuals in bite-size chunks, so you miss out on insights you only get when someone holds everything in their head at once.
You won't be able to have a small team / small company culture anymore. You have to be large, standardized, bureaucratic, catering to the least common denominator. And then make up for it with volume.