The CPS issue is because of litigation not protection. No one wants to be responsible for something bad happening.
Yes, they absolutely own their children more than the state does. I can’t believe there are any claims otherwise. Do you value the bond between parent and child and how special it is? Nothing should violate that. Not even the rare parent that is actually neglectful - meaning that should curtail the freedoms of the typical parent. And anyways, choosing to forego a vaccine isn’t abuse - on average it shifts outcomes very little. For example skipping a flu vaccine won’t change much.
A parental bond doesn’t overwhelm a child’s own rights as citizens and human beings.
Parents live in a society, even if it were a village, and there is no free pass to do just what you will if it crosses lines.
Collective health is one of those lines.
I think you need to spend some time thinking about how your idea of a just society is that child abuse is ok if parents do it.
In a just society they should have sole discretion. The current situation where kids aren’t even allowed to walk to school without CPS harassing parents, is because of this attitude where the state thinks it has any rights to your kids.