Life sucks in the best of times. I was not going to bring a human to the world so she would suffer, replacement levels be damned.
If I was unable to give my daughter a comfortable life, I would rather have no child.
I think many people would agree with this sentiment. If we want more people to have children in early adulthood, we need a major social upheaval so that people can achieve financial stability earlier in life.
Most people that seem overly concerned with fertility and population replacement, also happen to consistently vote against any policy that could nudge things in a direction where people would be able to achieve financial stability earlier in life.
My answer to that is a vague shrug.