I mostly agree with this, but I also have mixed feelings on it. Whenever possible, I think it'd be amazing to have one (viable) parent stay at home while a child grows up. My mom was able to do this & it was a really great experience for me growing up, so my frame of reference, having experienced it myself & having had it be a positive element of my life, means that I see it as a Good Thing.
However, my wife was a full-time nanny for some really wonderful families, where everyone's situation was unique. When I lived in the south, the cost of living was way cheaper and you could afford to have one parent stay at home. I live in the northeast now, and it's very difficult to not have both parents work, if one parent doesn't have an awesome-paying job.
So sometimes there are simply financial restrictions that dictate the situation, which means that the kiddo has to be watched by the grandparents. Other times, there are other factors involved. For example, my buddy couldn't stay sober to save his life - he was a great dad outside of his drug use, but his life was a wreck & he couldn't stop using, and fortunately his parents were available to watch the kids. It got so bad that eventually he got his kids taken away from him & the grandparents are now the full-time guardians, and those kids are in a waaaaaay better situation now than they were before.
Also, some people just don't do well as parents, but still want to have families & raise their kids well, and I don't think that involvement but managed assistance is a bad thing. I'm not saying that in a mean or negative way, but sometimes you get two highly-driven "power couples" who both have a strong need to be at work, and having a loving, caring nanny at home to mitigate two Type-A personalities can help
tremendously. People are the way they are, so seeing that situation in action kind of changed my view on things, to allow for more variation in different situations, while also getting good results.
Everything really boils down to the "it depends" principle, as applied on a per-situation basis. Sometimes you situations where have one or both parents pass away, or are physically/emotionally/mentally unavailable, and a family member or friend has to take care of the kids. I do think having a caring stay-at-home parent is a good thing, when available, and is a really good target to aim for. One of my friends is a "product of the system", as he likes to say, and was in foster care from a young age...from his stories, it was an
incredibly difficult experience for him in so, so many aspects.
I think that having a caring, dedicated person in your life growing up that you have daily access to is a huge benefit. Ideally, that would be a functional biological parent, but circumstances often dictate the situation, and you do the best you can given your set of constraints. And it doesn't just apply to babies & younger kids, either:
www.gsb.stanford.edu
But yeah, I think, in an ideal world, having one capable parent to stay at home with the kids would be something to strive for. But I also know a lot of single working moms who are doing a great job raising their kids with the resources they have available, and there are just plain a lot of people in really crappy situations. Growing up, my friend's mom died of cancer & they had 4 kids at home, so their sister had to bail from college & take care of them, because his dad had to work during the day to provide for them. Not an ideal situation, but that was their reality, and they all turned out fine!