My point isn't about engineers; the same can be said of architects or designers or even middle managers. If you have a team that you trust, having any number and grouping of them able to come together around a problem will produce results. A team being "flexible" does not make them "cogs".
You're looking at this from the perspective of a skilled professional, which is fine -- most of the HN audience probably does as well. But it's not the perspective I'm talking about. I'm talking about the perspective of the people who see skilled professionals as a problem, because their skills mean they can demand things like money and respect as a condition of employment. That reduces the CEO's flexibility to do things like take that money and put it instead into his own golden parachute.
Many organisations don't want to rely on a handful of supermen who solve all of their problems as such people may become indispensable and then demand higher wages or go to a competitor. They would rather break their processes down into a bunch of specialized tasks that require few skills so that new workers can be popped in and out quickly.
The wage level is somewhat orthogonal to this - doctors are generally interchangeable cogs, but they get paid well. The key point is avoiding single points of failure.
Besides there is a relatively small pool of people compared to the general population who are even capable of becoming doctors, not to mention the very long spin up time.
An analogy would be breaking down the tasks performed by a doctor into chunks that could be done in isolation by minimum wage workers.
Skilled professionals become more experienced at their jobs over time, they also have differing experiences and may have graduated from different schools etc.
This means that they will perform their jobs differently in ways that way be subtle and not easily quantifiable. So if you swap them out, things will change in ways that may not be easy to predict.
On the other hand a minimum wage worker is more likely to perform a job that requires a total training of 1 hour or less and they are likely to hit a ceiling in terms of productivity within a week. There may be minor differences in output, but these are easily quantifiable and if you have a large enough labour pool to draw from can be solved by saying "fire anybody who does like than X per hour".
I think the main difference probably comes down to medicine having more procedures and redundancy built in because you can't let a patient die when a particular doctor is not available.
OTOH my older relatives definitely complain about/praise individual doctors for bedside manor , professionalism and misdiagnosis etc.
Medicine is high skill, but the outputs are fairly homogeneous. Homogeneous output is what makes workers interchangeable cogs, not skill level.
Which would be amazingly hard for all the same reasons writing a program to replace a doctor would be amazingly hard.
In a company like Walmart, which is entirely predicated on the existence of interchangeable minimum-wage workers, the main component they can't replace is the process all those workers follow which results in a working store. That's the software run by all the human hardware.