askchapo

Great answers in this thread already so I'll talk more generally:

When we try to understand the world by fitting it into conceptual boxes, we are necessarily reducing it to simpler, more digestible models. This process is a double edged sword in that it allows us to understand and communicate ideas about something that's otherwise infinitely complex, allows us to brush over a million other variables so we can focus on key ones of interest. But at the same time these models are not reality, variables are being ignored or de-emphasized, leading to potential inaccuracy (rather than merely imprecisions). Additionally, that human component is prone to being influenced by bias/ideology.

So in the multitude of concepts clustered around the word "materialism", some of them may ignore or de-emphasize variables that actually have meaningful influences, resulting in models that are too reductive and that might lead one to make choices that don't have the desired and expected outcomes.

Class reductionism is one you'll commonly read about in Marxist circles. Mechanistic materialism (as opposed to dialectical materialism) might be another. But as with most categories, the lines are fuzzy and sometimes arbitrary. Two people who ascribe to materialism might call each other vulgar materialists because they disagree on which variables to de-emphasize or where to draw the line between idea and material. Similarly among diamats and what constitutes base versus superstructure.