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.