There were countless socialist philosophers in Central Europe during the 19th century. However, no modern socialist-leaning individual has any idea who any of these individuals were. The only socialists anyone knows are Karl Marx and Friedrich Engels. Now, Marx and Engels were not only super controversial but were not even that popular in Germany for their time. Their contribution to socialism was to take away the moral and ethical question of the first principles of socialism and apply a pseudoscience that everything is economistic. The Marxist theory that history is driven forward by the means of production.
The Authoritative sources for modern socialist thinkers
Orthodox Marxists will state that Marx and Engels would be disgusted at the state of the modern Left in the West. Which is totally true but the archetype of a Leftist is still there. A trust fund kid who owns a factory which was Engels and a Jew. A Jew who has connections to the media, bankers, intellectual circles, and a Jew who has connections to other Jews. Even though Marx's parents were Protestant converts, but his children were adamant Zionists.
If you read Marx and Engels private letters they see the working class as rabble. "Don't mix with the rabble down there" they would say as Engels is looking down as the factory owner. Engels himself came from a wealthy family, owned a factory, and had proletariat wage workers that he didn't do anything for. Marxists will scramble to the defense of Engels despite this. They will tell you it is because Engels was engaged in a theoretical struggle. That Engels was still apart of the overall capitalist structure and until the structure changes he couldn't treat his proletariat workers better. Which is an absurd defense of Engels and how he treated the workers in his factory. Engels shares this in common with the lion's share of modern-day Marxists. Who for the most part are urbanite bugmen that take up these ideas because they are in vogue in intellectual circles. They espouse these values and don't seem to have a problem not living up to them.
Contrast Engels with the early Welsh socialist theorist of Robert Owen who was also a wealthy factory owner. Robert Owen was undeniably against child labour and he banned child labour at his factory. Mr. Owen also lobbied the British government to abolish child labour. Mr. Owen engaged in profiting sharing and created his industry concerns into communes as quasi-socialist experiments for his workers. Karl Marx and Friedrich Engels never did such things and were not fond of mingling with the proletariat. They were in their own intellectual bubble.
Wealthy Urbanite Bugmen love to LARP as Socialist
If you look into the Pre-Marxist gentile socialists. They experimented with these theories by putting them into practice. You see experiments with different modes of social organization in an attempt to create a community along a complete universalist, egalitarian lineation. The North American Phalanx commune based on Fourierist theory, and the Owenite Utopian communities in the UK and US based on Robert Owen's theory.
Orthodox Marxists will also state that the Frankfurt School was an aberration of Marxism. The Frankfurt School did oppose the USSR, and it did set the stage for the American ideology. However, the goal of the Marxist project is the destruction of all categories. To clarify what I mean by categories is the destruction of borders, nations, ethnicities, the family, etc. Friedrich Engels wrote the book, The Origin of the Family, Private Property and the State, in which he states that the family is a form of an oppressive structure that should be abolished and withered away. Basically, what Marx's end goal is some kind of libertarian anarchism. It wants the withering away of all structures and the only reason to use the State, the dictatorship of the proletariat, is to destroy all structures. The church, the family, the concept of nations, ethnicities, and so on. Karl Marx would not be that upset about some of the people claiming to represent him today.
SJWs are the true inheritors of the original goals of 19th century Marxism than Tankies
When Orthodox Marxist state that the Frankfurt School was an aberration of Marxism. When you embrace an ideology like Marxism. On some level, you are too inside of those ideas and taking them seriously on their own merit. When you have a real understanding of the Jewish Question. You realize that Jewish intellectual movements are Jewish strategies to break down gentile societies and make them vulnerable to be dominated by Jews. Let's look at who promoted Marxism, what happened, and what does it look like in its modern form. Jewish intellectuals focus on developing strategies under the mask of ideology in order to attack pro-social elements in gentile societies.
If you are ideologically a Marxist that took Karl Marx's idea seriously about a global communist revolution and a global communist state. You would realize that Marxism was a total failure. However, when you think about it from the perspective of Marxism being a tool for Jewish power. It was actually a great success. You go from the working-class revolution and then moved into the sexual revolution. For one, the sexual revolution really hit America in the 60s. It previously hit Europe & the Soviet Union in the 20s. The working-class revolution and sexual revolution were all apart of the Communist revolutions in the 20s. You can see the build-up to it in the late 19th century.
My theory on Marxism in the 19th century was that Jews incorrectly saw the proletariat as a possible vehicle to destroy gentile institutions. This theory was proven wrong in the 20th century, and I'm convinced that if Marx could have seen the outcome of the 1920s/30s. How nationalists were able to win back the Proletariat to defeat the Communists. Marx would have done exactly what the modern left has done. Which is to de-emphasize class struggle and re-emphasize cosmopolitan identity-based class struggle. The approach of minoritarianism of organizing blacks as the new proletariat, organizing immigrants as the new proletariat, and organizing gender/sexual minorities as the new proletariat. Marx would have updated his theory like his claimed inheriters have. The way to understand Jewish socialist theorists is that Jews are a block of people trying to concentrate power.
What Marxism has always been about