Let us remember that Marxism has to do with the unequal division of wealth and power in society, and looks at the mechanics of the system where the working class or the subordinates of society are kept powerless and dependent upon the higher classes. An appropriate way to begin to answer this question is to think about the character of Krogstad, who is employed in Torvald's bank. When he comes to speak to Nora in Act I, he talks about the desperate situation that faces him and how he has rejected his illicit past activities for responsibility and a sure job:
But now I want to drop all that. My boys are growing up. For their sakes, I'll have to win back as much respect as possible here in town. That job in the bank was like the first rung in my ladder. And now your husband wants to kick me right back down in the mud again.
Krogstad is therefore depicted in the play as a worker suffering unfairly because of the power of his line manager. He has dependents in the form of his "boys," and a real desire to reform his character and do well in the world. The way that he is given no power in this world and society and all the power is concentrated in Torvald would be something that Marxists would analyse greatly.