[aimixin answers a similar question in r/genzedong]

Saying Marxism isn't about morality or excludes morality isn't meant to say Marxists are immoral or amoral. It's sort like, computer science doesn't talk about morality, but that doesn't make computer science immoral, or software developers amoral. They're just separate topics.

Marxism is meant to treat socioeconomic development as a material science. Biology and chemistry can inform doctors on how to make medicine and what medicine to prescribe people. But biology and chemistry themselves do not prescribe anything. Prescriptions require some sort of stated end goal, which is subjective.

Stalin says something similar in Economic Problems of Socialism in the USSR, where he points out that political economy is the study of objective laws of social development which are outside of the control of the government, that the government's policies are not equivalent to political economy as a science but are prescriptions informed by the science.

This is what Marx had to say on the subject.

Communists do not oppose egoism to selflessness or selflessness to egoism, nor do they express this contradiction theoretically either in its sentimental or in its highflown ideological form; they rather demonstrate its material source, with which it disappears of itself. The Communists do not preach morality at all.

They do not put to people the moral demand: love one another, do not be egoists, etc.; on the contrary, they are very well aware that egoism, just as much selflessness, is in definite circumstances a necessary form of the self-assertion of individuals. Hence, the Communists by no means want to do away with the "private individual" for the sake of the "general", selfless man. That is a statement of the imagination.

—Marx, The German Ideology

In some sense, you can argue there is a Marxist morality, but not from the perspective of subjective prescriptions, but merely an attempt to explain an objective origin to already existing morality. Such as, the origin of liberal viewpoints, which are heavily steeped in morality, clearly emanate from the capitalist mode of production. One could also argue a socialist society would produce a different kind of morality, but this would not be a prescription but would have to be demonstrated with evidence.

I don't think there is any reason to try and force morality or ethics into Marxism. Marxism does not need to be some all-encompassing worldview. It's fine to get your beliefs and views from other sources. I am influenced by many writers, many of whom are not Marxist. I don't get all my ideas from one source, I don't feel a need to somehow make Marxism all-encompassing.

I mean I'm not a philosopher or an expert but I don't think you can read Capital and not conclude that Marx is at least partially motivated by moral outrage. Page after page of examples of children doing dangerous and exhausting work, rigorously documenting just how little food workers are getting, he even waxes poetic at times to make it clear how bad he thinks the capitalists are when they defend these realities as necessary or moral.

It's not strictly necessary for the theory to be useful (hell, it seems like the worst capitalists clearly understand the theory, even if they don't articulate it in the same terms) but Marx isn't, in my opinion, neutral as to which side is good. Even if he would say it's best to assume a scientific detachment I think he has picked a side, and not merely for material reasons.

From Engels’ Anti-Dühring, Pt. 1, Ch. 9:

[…] we find the modern-bourgeois morality and beside it also the proletarian morality of the future, so that in the most advanced European countries alone the past, present and future provide three great groups of moral theories which are in force simultaneously and alongside each other. Which, then, is the true one? Not one of them, in the sense of absolute finality; but certainly that morality contains the maximum elements promising permanence which, in the present, represents the overthrow of the present, represents the future, and that is proletarian morality.

But when we see that the three classes of modern society, the feudal aristocracy, the bourgeoisie and the proletariat, each have a morality of their own, we can only draw the one conclusion: that men, consciously or unconsciously, derive their ethical ideas in the last resort from the practical relations on which their class position is based — from the economic relations in which they carry on production and exchange.

But nevertheless there is great deal which the three moral theories mentioned above have in common—is this not at least a portion of a morality which is fixed once and for all?—These moral theories represent three different stages of the same historical development, have therefore a common historical background, and for that reason alone they necessarily have much in common. Even more. At similar or approximately similar stages of economic development moral theories must of necessity be more or less in agreement. From the moment when private ownership of movable property developed, all societies in which this private ownership existed had to have this moral injunction in common: Thou shalt not steal. Does this injunction thereby become an eternal moral injunction? By no means. In a society in which all motives for stealing have been done away with, in which therefore at the very most only lunatics would ever steal, how the preacher of morals would be laughed at who tried solemnly to proclaim the eternal truth: Thou shalt not steal!

We therefore reject every attempt to impose on us any moral dogma whatsoever as an eternal, ultimate and for ever immutable ethical law on the pretext that the moral world, too, has its permanent principles which stand above history and the differences between nations. We maintain on the contrary that all moral theories have been hitherto the product, in the last analysis, of the economic conditions of society obtaining at the time. And as society has hitherto moved in class antagonisms, morality has always been class morality; it has either justified the domination and the interests of the ruling class, or ever since the oppressed class became powerful enough, it has represented its indignation against this domination and the future interests of the oppressed. That in this process there has on the whole been progress in morality, as in all other branches of human knowledge, no one will doubt. But we have not yet passed beyond class morality. A really human morality which stands above class antagonisms and above any recollection of them becomes possible only at a stage of society which has not only overcome class antagonisms but has even forgotten them in practical life.

No, there is a clear political goal in Marxism. It isn't scientific analysis for the sake of scientific analysis. It's virtually impossible to read anything Marx wrote and not come out of it completely sympathetic towards the plight of the working class and view the ruling class with complete contempt. "From each according to his own abilities to each according to his needs" is a very clear moral prescription. He wasn't describing how people living in a bygone communal society behaved but prescribing what people living in a communist society ought to behave. Forget about being a good comrade, you'll go far towards being a good person if you start applying this moral principle to your life and cultivating this moral principle towards other people in your life.