I think ideally most families should be able to survive on the income of one parent, regardless of which parent that is. But I'm not sure how to get there, although I think the problem is closely tied to wealth inequality.
I also think in a better world, it would be practical for both parents to work, but work fewer hours, each working 20 hours a week. But in the US at least that generally isn't practical because most such jobs don't provide health insurance or retirement plans, and are typically very low paying jobs.