I think the problem is that marxism (small-m) wants it both ways.
It wants to establish a functional relationship between classes and economic outcomes, where class is defined by relations to production, and on the other hand it wants to paint the working class as immiserated, inviting sociological hair- splitting about what level(s) of income and wealth signify working class.
mbs
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CB: Marxism has never been shy about asserting that capitalism has contradictions. This "marxists having it both ways" is pretty much a contradiction within capitalism looked at from the angle of it being discussed by anti-capitalists. Also, Marxists emphasize ownership relationship to the means of production, but this has never meant ignoring the poverty of the relative surplus population/reserved army of unemployed, or failure to acknowledge different income strata in the working class or attention to the poorest and most oppressed sectors of the working class.