Unless the capitalist is actually involving the worker in false contract, no, he is not "giving back just a tiny fraction" of what the worker produces.
We create programs in my company. Programs for a huge financial corporation and that facilitate billions in operations around the world every day. But I am not producing billions. I produce a very tiny fraction of that. The sheer complexity and the number of people and talents involved to produce that in a concentrated effort is what produces it. CEOs make far more money not because they exploit us, but because they have something that most people lack: political connections and a social network that are the oil of this big machinery, together with some strategic vision in different levels of competency.
This was something hard for me to understand. But the ultimate power, the ultimate restricted resource *is* connections. And *any* distribution system be it of water, electricity or money requires that some "hubs" accumulate more of what is being distributed. The real social function of wealthy people is first and foremost to invest their money wisely in prosperity creating ventures. That is what will level up the quality of life of everybody, including the poor.
Something that will never dissappear though, is the fact that a few people will have vastly more than the majority. Pray to God they never dissapear! This would be like loosing all the dams and water towers dissappeared.
The fact is that the poor in the developed world, or even in developing countries like Brazil, liver far better than their ancestors. They live more, they experience more. Compared to the billionaires, they experience less, but compared with the past it's far better.
I use to say that the left hates the picture of the social pyramid, and would like to make it a narrow rectangle, with everybody more or less on the same level. My stand is that the pyramid is a natural, desirable shape, and that it's not the form that has to change, but the pyramid must go up in the axis of quality of life. So what if the ridiculously rich can pay for pornographically expensive experimental treatments to make life longer? They're just making themselves the guinea pigs of humanity. Sooner or later that treatment will become stable, safe and accessible. That's why the health system must have a private sector and there must be treatments "accessible only to the rich". There are things that are too expensive and experimental to be made universally accessible. Today we have an average life expectancy of 75. Maybe the rich are at about 80. As health progresses the rich will experiment with novel initially expensive treatments and have a life expectancy of 110.. the poor will have a life expectancy of 90 and there will be some protester complaining the poor don't have access to the new taquionoscopy technology.
The rich are an important and useful part of society, even with their sins, as long as their wealth is part of a healthy financial system that is not artificially created by imposition of force.