First of all, the problem of the wealthy gets resolved with death. History shows that 93% of family fortunes disappear in three generations. Even exceptions, like the Ford Family, one the wealthiest in America at one time have only 20% of the wealth in inflation adjusted dollars that they once had. We still recognize the name, but the Fords are not in the same league as the Zuckerbergs, Bezoses, Gates, and Buffet.
Most wealthy people have in fact provided us something we want and are willing to pay for. Mark Zuckerberg has given us "free social media" access in exchange to subjecting us to advertising. We accept that contract willingly and have made him a billionaire.
Several professional athletes have never sold us anything, they simply negotiate to perform and let us watch them and some have acquired fortunes in excess of $500 million. Others allow companies to put their name on products and we pay a premium to have their name on our bodies. They didn't take anything, we offered them money to bask in their identity.
So, with the exception of people that earn their fortunes illegally, most of the wealthy have become wealthy because we like what they have created.
Regarding how goods and services are distributed in society is a more difficult issue. Science, history, and every other attempt to understand why human beings work for "profit" and not for strangers has resulted in the conclusion, that a society based on altruism and people sharing equally what they produce will end up starving. Even socialist countries end up denying entitlements to citizens that don't work.
Families and small communes seem to make it work, but once you move beyond that, altruism does not work. Instead, any attempt to create a socialistic society has simply replaced an elite class who got rich making things with an elite class who got rich controlling the distribution of goods and services.
The problem is without rewarding people to make things, there is nothing to distribute. And so, the lesser of two evils is to allow people to become rich making things and avoid second tier of elites who make their fortune controlling how things get distributed. Sadly, we have both groups in America... the second group is primarily comprised of powerful politicians.
Human society operates best under a self-interest economic model (you get the benefit of what you make) modified by adding a social safety net for those who need help... up to a point.
How do you know when you reach "that point".
As soon as a politician claims that someone is not paying their fair share... you have passed the point of altruism and pushing coercion in order to force greater centralized distribution of goods and services and power for the political elite...
So, the only moral and ethical reason to allow the creation of so much wealth in the hands of individuals is that society works better than if we don't. You can attempt to "claw back" some of their wealth for society's social safety net but go too far and you actually end up impoverishing the poor even more. Several states in the US and nations in the world have learned this the hard way. Look at what happened with the "millionaire's tax" in France and why it failed.
