In cases like that, it is often much more helpful to discuss the actual substance(s) of the topic(s), such as equality, property ownership, markets, exploitatio

In cases like that, it is often much more helpful to discuss the actual substance(s) of the topic(s), such as equality, property ownership, markets, exploitation, and philosophy of history (all of which have separate articles in SEP) than to try to dissect the incredibly broad, vague, and diverse set of ideologies that "Marxism" is. SEP has articles on a number of other people who took Marxism and ran with it in different directions, such as Georg Lukács, Herbert Marcuse, and Jacques Derrida, as well as critical theory as a whole. It also has a bunch of other articles on strands of feminism that were deeply influenced by Marx. It is the mark of an important thinker that he shows up all over the place in all sorts of topics. Whatever you think Marxism is about, I'm pretty sure you can learn about it on SEP. But you can't do that by reading a single article, any more than you can learn a major web framework by reading a single file. But I do admit that SEP would benefit from more hyperlinks to make related articles more discoverable.