If current trends hold, within a few years less than half the U.S. adult population will be married.How can she come up with contradictory positions? If you read the column, her focus is almost exclusively on the impact it has on adults. Children are only briefly mentioned relative to the instability of cohabiting and divorced households. There's less stability. And in the case of divorce, greater poverty.
This precipitous decline isn't just a social problem -- although it is that, too -- it's an economic problem. Specifically, it's an income-inequality and economic-mobility problem.
The steadily dropping marriage rate both contributes to income inequality and further entrenches it.
Why does she fail to see that the importance of family structure includes the inclusion of the man and woman in the marriage relationship? I suspect, because she's lost sight of the importance of children. Marriage has become the proverbial "loving committed relationship between two adults" which exists to satisfy the desires of adults whatever those desires might be. If children are important to fulfill those desires then by all means have children. If they're not, then definitely don't have kids.
Of course, this attitude is leading towards a crisis in the West - birth rates well below the replacement rate. This will lead to a significant socil crisis over the next few decades.