Allow me to explain. There are characteristics people possess that make them better or worse at "capitalism" that go beyond simply being willing to work. Examples would be the most menial and physically demanding jobs being the lower paid jobs. Capitalism works best for those with education, skills, genetic traits, family ties, and a strong work ethic. So, while willingness to work is a huge factor, it is not the only factor.
capitalism works best when it is compared to any other system.