you can see it not working. you can see it in the millions unemployed, losing their houses, uninsured, dropping out of education.
the apologists will answer, that there is a temporary glitch, service will return to normal soon.
not good enough.
when one link of an anchor chain fails, and the ship is lost, we don't say, "only one link failed, most of the chain is perfect." when a car works just fine for 100 yards, but then stops until it cools off, you don't say "it works most of the time."
aside from periodic failure, the system doesn't even pretend to work for everone. imagine throwing people into the garbage can, because they are 'unneeded.' america is a nation that views its people as a commodity, to be bought and sold, and thrown away, as required.
an economic system that can't even pretend to work all the time for all the people is no system at all, it's a label for an economic free-fire zone.
the fall-back position for the apologists of capitalism is that it is the best system available. best for what? best for who?
it's not best for the nation, because the lost production and skills can never be replaced, they are a permanent scar on the economy. it may be best for the '1%' to destroy any savings in the lower classes, as it makes them humble and pliable, but it's not best for the 99%.
and there are other, better systems, without even getting into total socialism. many nations in europe achieve better results in the 'civilization indices' by simply injecting some worker control into production and commerce.
this can't be done in america because the sacred constitution flash-froze american society in the legal attitudes and customs of georgian britain. capitalism doesn't work, because it was never meant to. it was just a label applied to a bandit society ruled by looters and exploiters, the 'cosa nostra' of anglophone nations.