From my socially conservative standpoint, the left's problem isn't ignoring families, it's promoting a very narrow vision of what a family is. One gets the impression from many left-liberal activists that the ideal family has 1-2 kids, lives in a city, and has both parents working full time.
For example, almost all the family/childcare policy I've heard from the centre left lately is based around making paid childcare more affordable and increasing female labour force participation. The mother who wants to stay home or work part time or have four kids is ignored. Similar themes are found in urban planning. I agree car culture has run amok as the next liberal, but I can't quite shake the notion that for some leftish folks that we're all supposed to live in 1 bedroom condos in downtown highrises.
I find this very interesting, since I imagine most socially liberal people would say the same thing about social conservatives.