An Inspector Calls focuses on the cons of capitalism. The plays makes the point that even if they are not legally responsible, the Birling family and its soon-t0-be new member, Gerald Croft, are morally responsible for the death of a poor young woman whose goes by various names over the course of the play.
The wealthy Birlings use the power of their money to oppress this young woman. When she agitates for a higher, living wage, Mr. Birling fires her from his factory without a good recommendation, making it hard for her to find another job. When she does land a job working in a department store, Miss Sheila Birling has her fired for rudeness by threatening to withdraw her family's business. Instead of merely helping her, both Gerald and Eric Birling trade money for sex. Eric leaves her pregnant and desperate so that she commits suicide. Finally, Mrs. Birling denies her charity, saying the father (not knowing he is her own son) should provide for her support.
The play shows how, under a guise of respectability, the self-centered Birlings and Gerald use their money to crush an innocent woman trying to survive. This is a scathing indictment of capitalism.
On the other hand, though outside of the point of the play, we can see that capitalism works very well for the privileged, allowing them a comfortable life. A con of socialism (not stated in the play) might be that it takes away the incentive of people like the Birlings to work hard to get ahead. A pro of socialism, however, would be the safety net it would provide for everyone, including the Birlings, who might one day face poverty or misfortunate in a precarious economy.