If you want to get pedantic, we could more precisely define the upper-class as those who extract value from others, and the lower classes as those from which said value is extracted from.
Were we to push that to the extreme, the only upper-class at Goldman Sachs would be retirees, either as direct shareholders or as beneficiaries of some pension fund. Even if they were lower middle-class Americans living in an old aging house they can’t afford to fix.
That would be the Value Extraction definition of Class.
Others would argue that class is more diffuse, and that one’s class depends more on their family's history, where they went to school, and who they know, than on how much they have. Which is a valid point.
That would be a Social Capital definition of Class.
I doubt however that anyone would consider a street-sweeping former Emperor (eg Piyin), or some penniless heir to some old industry dynasty as still belonging to any sort of upper-class.
Meaning the actual definition actually is some fluid mix of the two. That and probably some other definitions I’m not even aware of.
> In the modern economy, capital owners are reliant on a class of non-fungible white collar workers that bring their own human capital.
It’s nothing modern. Capital owners always have, since the first scribe, and probably before that (see Japan’s former hordes of perpetually desk-bound samurai).
Still, let’s entertain the argument. I’ll use, and I’m truly sorry for that, a tired analogy.
In the modern world, many people are reliant on many different types of usually non-fungible pets and somewhat fungible, depending on who you ask, animals, for many different purposes. Some of which bring their own highly sought-after hard-earned skills.
Let’s limit ourselves to the oh so tired dog analogy.
A person and their dog have myriad common interests. Those interests are, in many cases, in opposition to those of many other people and animals. Even more so when said dog is considered a family member, serves as a guard dog, as a shepherd dog, or is specialised in drugs detection.
Does that make them equal? Does that change anything to the fact that one is extracting value from the other, and often only pays them back in dog food, usually made from our food industry’s literal scraps and refuse?
So yes, I agree with you: there’s no simple and definitely no simplistic definition of class.
I am still convinced however that, in the specific and limited context of the comment I was replying to, the one I used was good enough.