Marxism implies a dialectical philosophy focusing on economic primacy (yes I know this is broad), and usually implies a dialectical method by way of Hegel

Post-structuralists, e.g. Deleuze are anti-Hegelian.... Freud, Lacan, Marcuse, view society through a psychoanalytic framework as opposed to economic, though all are “Marxist”, and Nietzsche, who is not a leftist is completely anti-dialectic, as with Bataille, who is an ultra-leftist of the Radical Evil variety, like Sade

Anyway, point is there’s plenty of philosophy that is either leftist and not Marxist or not leftist but still foundational for leftists (Nietzsche? Spinoza?)

Gilles Deleuze was a French philosopher who, from the early 1950s until his death in 1995, wrote on philosophy, literature, film, and fine art. His most popular works were the two volumes of Capitalism and Schizophrenia: Anti-Oedipus and A Thousand Plateaus, both co-written with psychoanalyst Félix Guattari. His metaphysical treatise Difference and Repetition is considered by many scholars to be his magnum opus. An important part of Deleuze's oeuvre is devoted to the reading of other philosophers: the Stoics, Leibniz, Hume, Kant, Nietzsche, and Bergson, with particular influence derived from Spinoza. A. W. Moore, citing Bernard Williams's criteria for a great thinker, ranks Deleuze among the "greatest philosophers". Although he once characterized himself as a "pure metaphysician", his work has influenced a variety of disciplines across the humanities, including philosophy, art, and literary theory, as well as movements such as post-structuralism and postmodernism.

Deloser

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