But it is rational for any individual to not work as hard, because he will bear less of the cost of that work, but still realize the same gain
They wouldn’t realise the same gain.
More valuable work is better paid. Skilled management is likely to get better pay than menial work. Dangerous jobs get better pay than safer jobs.
You are not allowed to become rich by exploiting others, though.
The benefit is that there’s at least a goal that will benefit the poorest strata of society.
Capitalism doesn’t address it at all. It’s every man for themselves and fuck everyone else. That’s textbook recipe for sick societies, like all capitalist societies on the planet. None of them work for the poorest of the people, none of them attempt to do so.
It’s crisis after crisis, with random economical meaningless inflation fear mongering to get people to hate their fellow workers. To compete for an ever decreasing pool of jobs.