No, capitalism is not a belief system. That’s just marxists’ image of capitalism.
Capitalism is when a free market results in some people deciding to get wage jobs instead of being entrepreneurs. When you get a worker class, who accepts the trade of more income security for less potential profit, ie when there are “jobs” in the private sector, then you’ve got capitalism.
Because capitalism is based on free markets, ie markets where people have choice of how they engage, a successful capitalist is one who resists short term greed in favor of long term profits.