It's in everyone's best interest to have fair, just economic systems. Good systems where wealth is more strongly linked to economic output rather than birthrights lead to more prosperity and justice for everyone. Too much wealth inequality hurts growth, and it also creates political inequality that can create a feedback cycle that worsens the problem. Social justice and economic justice are inexorably linked, if one group has all the power, bad things happen.
Also, you clearly live in a very wealthy neighborhood, but many people are struggling. Even if people aren't struggling, the "you can't complain about anything being injust because someone, somewhere is in a more unjust situation" is an absurd line of reasoning.
I know I'm not struggling and I know that other people are. I was just trying to demonstrate how silly it can look when people complain. No matter how much people have they're always comparing themselves against these impossible outcomes. I don't see how others having more in any way diminishes what you have.
Also, why can't owning a hot dog stand that pays the bills and puts your kids through college be considered the American Dream? When did that turn into yachts and trips to the International Space Station?
How so? China is still, to a great extent, a command economy. The usual rules don't apply. The Chinese government can create all the artificial growth it wants and is not directly answerable to the public.
One could point to basically every country in Africa and many in Latin America and Asia for support of the assertion. One counter-example (not that I agree China is even a counter-example in this case) doesn't disprove the theory in social science. There are always weird exceptions.
There are a million other confounding variables, but you can also track a reasonably strong correlation to income inequality and growth rates in the US over the past several decades.
Also, you clearly live in a very wealthy neighborhood, but many people are struggling. Even if people aren't struggling, the "you can't complain about anything being injust because someone, somewhere is in a more unjust situation" is an absurd line of reasoning.