The problem with this kind-of-definition is that it doesn't explain what makes capitalism unique.
Slavery and feudalism also percolate wealth upwards, and, relatively speaking, capitalism provides more goodies to more people. You risk landing on a situation where, like Nietzsche, you believe injustice to be ineradicable, and to just defend capitalism as the best of its ilk. If you insist on a simplistic and moralistic explanation, people will quickly turn on you when they realize something's amiss.
As the essay explains, making a deeper study pays off.