Capitalism might be said to serve as an adequate economic system if it provides, at least to those who work, sufficient goods "for carrying on the business of common life."
Capitalism does not do this, as evidenced by people starving to death every single year, and many children raised so malnourished that they are doomed to a life of ill health and (I think I read) diminished mental capacities. Therefore, capitalism is inadequate.
There are external forces, droughts and storms, which make food distribution difficult, but no one can argue that the existence of droughts or storms are anything new, and yet capitalism, generally speaking, sees no profit from preparing for such eventualities, and, in fact, there is often profit found when situations of scarcity occur.
There are also internal reasons why capitalism might not do as well as it could. Unfair trade is commonly practiced by the largest companies, and seems to follow Thucydides' formula "the strong do what they can, the weak suffer what they must." Generally it appears that as soon as one sort of unfair trade is ferreted out, then another comes along. Those with vast sums will almost always be of the mind to spend great sums to enhance, or at least protect, what they have.