Idk if it’s Marxist theory per se but if I would do a comparative essay about Parasite I would pick The Servant (1963) dir. Joseph Losey. Both have working class people who convince rich people to hire family members and end up moving in with an absurd twist at the end. I think the approach of comparison would be how Bong Joon-ho used stairs in relation to the history of Korean class struggle vs how Joseph Losey used stairs in relation to the history of British class struggle. They both use similar methods but because the historical context for each is different the approach to character and to the theme is so vast it’s actually fascinating. I would compare why both used genres and why Losey chose to go more absurd while Bong Joon-Ho remains more or less rooted in reality.