The whole point of social structure is for society to be fairly stable and propagate itself. The means by which this occurs however needn't remain fixed. Most of humanity's existence has been in very small groups, trying to cope with issues which we now consider trivial (illnesses, resources), but with the rapid technological development seen recently we may well one day live in a post-scarcity society, which will cause our social models to change as well.
Even without a technological utopia, the concept of marriage has evolved with society. The current idea of a "classical" marriage in western society is one man and woman, but there are plenty of times in human history when men could take multiple wives, for example. I wouldn't say that society moving away from strict enforcement the "traditional" view of marriage is the result of political narcissism; to me this smacks of golden age syndrome (another fallacy for you

).
I do agree with you on the point of raising children properly in order for society to function well, although this needn't be done only inside marriage. I knew plenty of people in school who had difficult upbringings and as a result had real attitude problems, but this seemed to be more to do with a vicious circle of poverty, as most of these pupils' parents were in traditional marriages.