Like Marxism, the theory fails in reality.
* The high level of expertise simply is not needed to teach most classes.
* Institutional teachers are rarely as motivated to care for a child as their parent is
* When a child gets to the level where expert teachers make a difference, the homeschooling model allows the flexibility to pursue those experts where the institutional model is rigid and uses a one-size fits all approach.
One of my daughters was very attached to her mother. In a public school, that was a problem because in a room of 30 students, the teacher cannot give every student that kind of attention. The advice given by another homeschool mom was that it was a fantastic opportunity. Let the kid sit on your knee as long as she does educational activities. She will outgrow wanting to be right next to mom, but the education would benefit her an entire life time. It was great advice, and worked just as described.
FYI, that idea in that phrase has nourished socialist politics for a long time already!