I don't see the problem as Marx having the only deeper view of class, but post-Marx philosophy became the province of cowards and charlatans. Marx does present a particular vision of the world and history, but he isn't the only one who asked these questions, and Marx is a contributor to that milieu rather than the guru handing down pedagogical truths.
As for Origin of the Family, it's actually been pretty well discredited and regarded as an artifact, and wasn't even in line with anthropology at the time. Engels is one of many speculating about the early family, and lifts a lot of his basic material from an American anthropologist he references concerning the natives of America. He's also inserting some of his own peculiarities, Engels being a known womanizer and all. The usual line of argument against Engels' writing there is that the state existed in some form before Greece, and existed in other parts of the world. The Greek thought on the state was highly particular, but it isn't as if most of the world didn't have some political philosophy or theory. What is noted in the Greek conception of the state is its focus on the individual subject, where in the rest of the world the clan and the village remained recognized as a unit, and organized religion was more common in most of the world but the Greeks did not have any organized religion. What relgiion the Greeks did have was often superstititons vaguely resembling polytheism of the old type, and political thought concerning the state suggested a rational basis (and of course, the position of the philosopher and their system) rather than a religious or spiritual one. In India, religion and philosophy were one and the same and the guru was both a spiritual advisor in touch with the gods and the philosopher expounding on what the world was rationally. In China, religion had nothing to do with temporal authority and the Emperor was in the end just a man, which was emphasized in their political thought. We can speculate why it turned out differently, but republics are such a fucked up form of government that the Greeks were the first to really establish the concept in a civilized setting. The particular attitude of the state towards the family is a feature of the republican idea, rather than something inherent to the state's functions. The state at a basic level doesn't regard the family as anything, but philosophical ideas about the state desired to relate to individuals, and the Greek form of the state emphasized that particularly and explicitly. Abolishing the family is straight out of Plato's Republic, after all.
One persistent feature of modern socialism has been its attitude towards family life, and a drive to question the familial relationship and familial obligations in all ways. Free love wingnuts were always present among the left, and it is not for some arbitrary reason. Modernity and industry entailed social transformation, whether people wanted it or not. In the end, the social transformation was co-opted by the state and turned into what we got. It turns out abolishing the family unit doesn't actually work because children need to grow in a home, not in a state facility and administered a pedagogy of the state's choosing. The state goes out of its way to destroy any child it doesn't want, and the finished product of state education leaves much to be desired. We know that now, but Engels didn't know that, despite early experiments in this not really panning out. To be fair, it is an attempt to consider the origin of the family rather than taking it for granted, asking why the family is what it is today and how it is changing. Personally, I think humans will have to adapt on their own, and most won't adapt. They haven't adapted very well so far, unless they're a particular type of person who can inhabit a highly predatory society and somehow enjoy it. This is not a society that allows for a world where we have peace, and it won't be that for us. It won't be that for anyone for a long time, and those who are comfortable are in a world hidden from the rest of us. They do not struggle the way we do. They do not.
In hindsight it is easy to see how Marxism would turn out, if it did not consider the world outside of Marxism. I'd argue that was the point - jump in front of the emerging social transformation and co-opt it, and then ditch the people who didn't get the joke. Those who got what this really was have been in a fairly safe position, one way or another. Marx wasn't the only one - just one of many who stepped in to make sure the social transformation modernity suggested did not happen, except on the terms of those with the will to push it into their desired form. The worst thing for the ruling interest would be if someone stalled the ruling program by noncompliance, up to and including simply leaving that society and picking up the pieces from whatever is left. It was necessary to seed "working class intellectuals" who would steer the workers towards preferred outcome, and that's what we got. It's why the "working class philosophy" is so alien to actual workers - what the workers wanted was a very different project, which entailed never letting something like what we live in exist for a whole century. It's why the social transformation was fought bitterly, and the workers were told they could only imagine a reversion to the past. The future was to be controlled by thought leaders, and Marx is a contributor to that, for reasons that make perfect sense to him and those who imbibe the philosophy. They didn't unilaterally choose this, as if Marx is the only one trying to manipulate history, but Marx described the method by which it can be done, for good or ill. The problem with constructing ideology is that humans are not really ideological creatures in that sense. The imposition of ideology is only possible with a large preponderance of force, and it doesn't know any other solution. When you have a hammer, everything looks like a nail. The future as I see it in the 21st century is post-ideological and a rejection of this ideological imposition altogether. The result will be likely that the mask comes off and direct control will become the norm, made possible by advances in dissecting the body and mind. Those military scientists have been cutting up brains for a century and figured out a lot of stuff.