Most of the problems I would say are related to the modern isolated Nuclear family.
See that programmer sat next to you that is not a nice person? Well some kid had no choice but to have him as a parent.
Throw in a society that doesn’t value teachers and pays them below many other jobs and the kid spends all his day and evenings with no one to guide and nurture him or her.
Truly, the cause of all this suffering is not enough antinatalism. You've cracked the code.
There is no modern isolated Nuclear family. There's mostly broken homes now, and that is the root cause of most of the problems.
Certainly we are all an alchemical output of our nurturing environments and our intrinsic characteristics, and I don't dispute that we could likely dramatically lower the incidence of severe mental illness by improving our culture's capacity for care and solidarity. It's tough out there, for children and adults.