I understand what you mean about children crying on planes. However, I was on a lengthy overseas flight and the couple (from Switzerland) had their kids climbing over seats and just running amok on the plane (this was several years ago). Screaming and yelling...you know being kids. They didn’t even blink.
People need to plan carefully for children - a night flight when the child will sleep is good. Don’t let the kid nap right before the flight, etc. Lots of strategies that the goofballs just don’t think about.
I think I was on a plane from Amsterdam with those people ;-). Whatever the situation, there’s a difference between a child’s being allowed to cause an avoidable disturbance, and a child’s simply existing.
And you’re right - wise planning could help avoid or reduce many problems.