Huh, looks like I linked it incorrectly. Here is the link plainly:

http://www.abstraktdergi.net/this-ruthless-criticism-of-all-that-exists-marxism-as-science/

It's an essay by J Moufawad-Paul on how Marxism's status as an attempt at a scientific understanding of political-economy is its very foundation and must be defended, both from self-professed "Marxists" who disparage this element as well as liberal academics who do just as you describe, treating it as merely another "lens" and functionally as a sort of rhetorical flavor and roleplay rather than a method to understand the world:

My position, however, which is the position of multiple revolutionary movements and the great world historical revolutions, is that we cannot be ecumenical. Whereas today’s chic critical theorists uphold a variety of post-Marxist European theoretical tendencies so as to dismiss and castigate Marx, I uphold Marxism to castigate these theoretical tendencies. I am not claiming, to be clear, that we cannot borrow from some of the insights of these tendencies but only that, as tendencies, they are theoretically inferior to Marxism regardless of the latter’s purported flaws. Weheliye [a "post-Marxist" academic] reduces every European theoretical tendency to the same state of “white European thinkers [who] are granted a carte blanche” but, in this reduction, misses a key point: it is only the Marxist tendency that can account for and surmount this carte blanche, thus necessarily generating theoretical offspring critical of its erroneous aspects, because of what it is: a science.

That is, the reason why those of us who are committed to Marxism can and should uphold this commitment in the face of other theoretical tendencies is because the theoretical trajectory initiated by Marx and Engels, which goes by the name of historical materialism, was one that was scientific. Unlike the so-called “radical” theories generated by or drawn upon its discontents, historical materialism is not a mere quirk of the humanities based on some academic’s thoughts about reality translated into an intriguing terminological set. Rather it is a natural explanation of natural phenomena that has generated a truth procedure and thus falls within the gamut of science. And it is precisely this claim that has made Marxism the scapegoat of those theories that, from their very inception, have also sought to destabilize and usurp the very conception of a historical/social science.

I do think Weber and Foucault are quite interesting and can be useful, but they do not hold the same ground that Marx and his successors do.