You guys might need to clarify what it means to target mainstream economists, but I can provide a relevant example of how marxists might do such a thing. Marxists like to talk about how mainstream economists tend to reify social relations, which means taking particular concrete social relations at some point in history and instead viewing them as universal categories.

Yeah, I don't see how this isn't just misconstruing mainstream economists' analysis. Just because they make arguments or analyses of things which depend on social relations doesn't mean that they've made some kind of assumption that the social relations can't change. It's simply outside the scope of their analysis.

What makes you think that Marx's analysis of exploitation and value is arbitrary?

Because it depends on an alternative and arbitrary interpretation of relations and value which is not falsifiable by economic data, and merely asserting "I'm going to construe this as exploitation" isn't a good argument for anything.

Putting this to the side, Marx actually did analyze poverty and unemployment. Indeed, a lot of it was a direct response to Malthus' views on population.

Mainstream economists have accounts for structural unemployment as well. The difference is, in that version you can actually figure out how to reduce unemployment by increasing inflation or other sorts of measures. Of course fucking Malthus's views were incorrect, they've long been discarded by mainstream economists as well for other unrelated reasons, such as his failure to take into account rises in productivity and technology. But the modern explanations for wages and productivity aren't missing anything like that, and they don't rely on dubious assumptions about capitalists being engaged in some kind of deliberate behavior to make jobs obsolete.

Marx saw past this reification and basically said that these issues are the result of capitalists requiring a reserve army of labor (relative surplus population), which he describes in his analysis of capital accumulation.

How would this invalidate Malthus's analysis? Sure, capitalists require a reserve army of labor. You've given another way of interpreting the labor demand function.

Obviously if producers wanted to be generous and provide wider employment at the expense of profits then they could do that. That's not a difficult or surprising claim.