There’s a certain empathy that is hard to have unless you’ve gone through it. People without kids have a tendency to underestimate both how challenging child rearing can be and also how totally different kids can be. That ends up with people giving parenting advice as if there’s a single right answer when there’s no such thing. It’s why I said people with only one child fall into the same trap. Often they think that the way their kid was is how all kids are. But kids can be so amazingly different, and it’s hard to truly understand that unless you have a couple kids yourself and you can experience it firsthand. I don’t claim to know all about parenting, but I’ve experienced enough to know that I can’t give any other parent the right answer for how to raise their kid.
This very much reminds me of inaccurate perceptions people have of being a teacher since they've had so many teachers they get a sense that they are pretty familiar with the profession but most have only seen one side of it. Also analogous to the other point you were making, a difficulty in education research is how hard it is to come up with generalizable conclusions since each context can be unique.
