It's a very compelling argument, except that in practice it seems to evolve into access to resources being predicated on a) the ability to extract resources from the system via external factors rather than labor or contributions.
However, even if we agree that someone's gains were based on unfair rules, that's not justification for pilfering a family's nest egg. If we allowed them to accrue that money legally, it's theirs, and we just need to correct the loopholes and move on.
Dismantling the free markets and systems of exchange enabled by private property only results in shifting every advantage to a tiny centralized core (usually government ministers, bureaucrats, and their families and staffs) who quickly grow rich while 90%+ of the population becomes impoverished. It is simply not possible for any government to produce a sufficient central plan, no matter how well-meaning or knowledgeable the planners. The world's natural chaos doesn't allow for it.
We saw this tried many times in the 20th century and there's not one success story to come out of it. People must be free to make their own price and value judgments in an organic marketplace because it's the only thing that can adapt quickly enough to the real world, and the only thing that actually provides some advantage resilience to keep a dishonest, exploitative pirate class from pillaging the economy with stunning rapidity. Ask yourself why this clear fact is often misrepresented as its polar opposite, and consider the interests of the propagandists with reference to that misrepresentation.
There is too much inequality today. We should work to fix that, but no one seems interested in paying attention to the details that are necessary to do so because the propagandists are too busy whipping them into a frenzy about the need to confiscate the assets of the 1% and transfer control of that money to their friends in the government.
Mid-20th-century America seemed pretty damned successful, and it involved very high income taxes at the top, confiscatory inheritance taxes, and strong antitrust laws.
Nostalgia for the era of "Mad Men" seems bizarre to me.
Your philosophical approach seems to be inching toward an argument between the libertarians and the communists and their ideal policy on tax rats. I think that is kind of a false choice myself.
Biology will always place a limitation on the amount of labor that one can expend, and psychology, which is an only slightly more pliable abstraction on top of biology, limits it further. Humans are biologically programmed, as part of the survival instinct, to preserve as much energy as possible. They will only expend hard effort when they are convinced that it will provide them with tangible and necessary benefits (where necessary means that the brain sends rewards in response to the anticipated benefit).
Inasmuch as wealth refers to the ability to command labor, either directly (like hiring an employee) or indirectly (like paying for the work product of another organization's employees), there are real limits that can't be circumvented.
As automation and technology enable us to a) prevent or seriously impede natural corrosive processes that destroy our work product and b) generate more useful goods and services with increasingly-less dependence on human effort, I agree that "wealth", for the value of wealth that means access to conveniences and luxuries, will become more generally available as we continue to improve.
Basically, you're arguing that access to resources should be predicated upon a) the quantity of labor rather than its value; and b) that access should only last as long as the effort is continually expended (curious re b: how many days can one take off before access to resources is denied? what if I want to take a year off to focus on a business? what if you think my business is a sham and not a legitimate expenditure of effort? are some people entitled to resource access without effort, and if so, which people, and why?).
People who want to leave an inheritance for their kids argue instead that access to resources should be predicated upon a) the value of their contributions rather than the amount of labor; and b) access to any excess resources should persist until they are fully exhausted by the owner's willful use, without regard to the amount of effort involved in earning it.
Only one of these models scales, not just in a free society, but any society.
The perspective that idlers should not get to eat while laborers starve is solid, but the plans that have been proposed to resolve it are impractical. The fact is that to some extent, inequality and unfairness will always be around. That's due to the fundamental functions of the physical world that cause scarcity, not how nice or kind the people who surround you are, so just trying to make better people won't solve the basic problem of inequity (it may, however, prevent class oppression).