Honestly, here in Poland we use polonized names for the theorists and they were also polonized historically. Karol Marks, Fryderyk Engels, Włodzimierz Lenin, Józef Stalin and so on.

Including even some soviet politicians and more people presumably, but most just have their names phoneticized for polish speakers. If a guy is of a Polish origin, it’s guaranteed their name will be written fully in Polish. Like Feliks Dzierżyński and Róża Luksemburg for example.