The debate over idealism and materialism (which still lingers today, no doubt) is a product of the early nineteenth century when reductionist scientism collided with hegelian idealism (and not only that), the latter a bit extravagant perhaps, and we see the extreme reaction in the generation of marx/engels. But the debate is pointless now, and in an age of quantum mechanics almost ridiculous. The obvious suggestion in general is that both views are right and somehow complementary.
The marxist left is still mired in the morass of that dated argument and needs to move on. Inflicting this one those who wish to move toward socialism is both pointless and highly prejudicial. The prospect of imposing hard-core materialism of the early science era on the whole of thought has alienated so many potential socialists that one has to wonder at the boxed mentation created by the marxist legacy.
Source: The eonic model beyond materialism/idealism – Darwiniana – Darwiniana