If that's your qualification for a "failed experiment," the Atlantic slave trade proved Capitalism a failure before these people were born.
But I get your point, just substitute any of the human catastrophes of the nineteenth century.
There is a reason why slavery was abolished on the brink of capitalism birth. It's because capitalism depends on free trade, not just any kind of it - the freer the better it grows.
*freedom for the property owner. Which is why it can facilitate a slave trade, property is a limitation of freedom.
Well, thats kind of unsurprising, since all the actual attempts to implement “Communism” on a national scale threw out the prerequisites in Marxism on favor of the (notionally transitional) elite ruling class of Leninist vanguardism (an adaptation to allow bypassing capitalist democracy entirely, because—viewed generously—the Bolsheviks and their successors were too impatient for Marxism.)