My opinion has changed a lot on this with more life experience, and I work with families. I think the obsession to have marriage/well paid job/have bought a house is short sighted. There is sometimes a snobbery that goes alongside that. That it proves responsibility. But where does it end?
People often mention property on the tick list, but they really mean having taken out a giant loan and the ongoing pressure to never have a drop in income so they don't lose their house.
Some people mention travel, but travel can be done with your family or before retirement if you have children young.
Having children outside of the biological optimum age increases the risk of genetic disorders. As someone with older parents, I am neurodiverse, and so is my younger sibling. My older siblings are not. I see this pattern often and I do wonder if this is a reason (alongside awareness and change in DSM criteria) why rates of autism and ADHD are rising more than predicted.
Older grandparents are less able to play an active role in their grandchildren a lives, thus adding to the financial pressure of older parents, and the grandparents and grandchildren missing out.
Younger mothers in their biological prime years should not be judged and discouraged more so than older middle class mothers as there are pros and cons to the lives of the children equally.