Rich people hire people, rich people buy big ticket items hence indirectly creating employment, rich people donate to charities.
In a closed system with no automation, yes.
A closed system is a situation where nothing enters or leaves. Mathematicians and scientists, in particular chemists, work with "closed systems" all the time.
In a closed system with no automation, it really doesn't make one whit of difference whether or not anyone gets super rich in terms of the welfare of the economy.
In fact, it can improve the culture, because a non-psychotic person with more money than they need will start spending it on non-essentials, like cathedrals and fine works of art.
All the great stuff you see from old Europe was from rich "nobility" having more money than they could use, so they'd spend it building cathedrals and purchasing fine art, and because it took human labor to build the cathedrals and make the fine art, people got jobs from those with more money than they needed.
Now, picture the welfare of a medieval kingdom where the king would collect his taxes locally, but would only spend his money on cathedrals built in other lands by foreign workers, and would only buy art created by foreign artisans.
How well off would his people be? How long before he wouldn't be able to tax them anymore because they didn't have any money, because he spent it all away?
In a case like that, did the king being super-rich do anything good for the economy of the people from whom he made his money?
Today we have a financial equivalent in the form of big business. It draws profits from a population, and as long as it invests those profits back into the population from which it drew the money, then it will create jobs, insolong as it is humans and not robots doing the work.
If big business chooses instead to invest in a place far away, or if it chooses to invest locally but have the work done by robots, then the effect on the population from which the profits were drawn is for them to become poorer and unemployed.
So, today we have a situation where big business - aka the multi-nationals - are not spending the money back where they got it from...
Plus even if they do, they pay a few people a one-time fee to install some robots (aka automation).
They get away with it everywhere except for the part where China does what Marx recommended, which was use the Capitalistic system against Itself. Now American owes a Communist state hundreds of billions.
Seriously... ever notice how the only difference between an MBA and a sports hero is the design of their suit... yet they will not go to war like a soldier wearing a real suit does.
Now, let's suppose there is a one-world government such that the whole planet is a single closed system... where no matter where the money is spent back it's still part of the same system.
We have a planet overpopulated such that it takes 4.5 earths to make everyone alive today middle class.
Spread it around, and everyone is in famine.
Fear would cause mothers and fathers to pull back, and only two countries have the self sufficiency to do that: Russia and Canada.