I think you're misreading what the OP is saying and you two are actually in alignment. They are not saying the nuclear family is an improvement on the multigenerational household. They are saying that the nuclear family is better than what we have today with divorces and single parent homes becoming increasingly common.

The degeneracy is from multigenerational to nuclear and from nuclear to less than nuclear families. Many people who are marxists typically celebrate the demise of both multigenerational homes and nuclear families because the family unit was seen as an opponent of socialist goals.