This is a complex question to answer because in answering it, one is made aware of their own predisposition towards capitalism.  If we say that Jurgis was not successful in protecting his family from harm, then, to a certain extent, we capitulate to the notion that somehow people like Jurgis failed in the capitalist system.  This cannot be entirely accurate because the odds were stacked against him from the very start.  While he might wish to "work harder," in the end, he is always going to be challenged by a system that favors owners over workers, that favors wealthy industrialists or entrenched individuals in the power system over those who are deemed outsiders.  This might be why we can say that Jurgis is not entirely successful in his attempts to protect his family from harm, but there was not going to be much chance of this given the condition into which Jurgis was placed.  This might be deliberate by Sinclair in suggesting that a capitalist system that is not going to hear the plight of workers will always be one where loved ones are placed in tremendous harm.  When Jurgis carries a pregnant Ona through the snow to the hospital with no plausible health care in sight, it might be Sinclair's profound statement about how all families are under siege from the capitalist system.