Neoclassical Economist Claims Capitalism is a Rational System

A Marxian interpretation of Mordor’s economy by Michael Roberts is that crisis is the result of the tendency of the rate of profit to fall. At the same time, the psychological states of individuals who make choices is irrelevant. But in the la-la world of neoclassical economics the economy depends not on decisions made by capitalists, but rather is based on the  individual choices of consumers being rational. But if rational choices were all that was involved then why do capitalists need advertising? Capitalism is an irrational system from top to bottom!