I mean this in its specific technical and economic definition. Childcare is low productivity in that no matter how much capital, technology, and mechanization you throw at it, one adult will be able to care for a limited number of children, and that limit is not all that much higher than what a parent could do. Infant childcare, for example, is limited by law in many jurisdictions to no more than 1 adult per 4 children, and if you've ever cared for an infant, you'd know that limit is pretty inherent to the job itself. Through Baumol's Cost Disease [1], this implies rising costs in these sectors and an increasing percentage of employment devoted to them.

That these sectors are necessary was part of my point. If the parent isn't doing the job, somebody else is; you can't just eliminate or automate the job entirely.

[1] https://en.wikipedia.org/wiki/Baumol_effect