I think it's a combination of nature and nurture
We know through research into ACEs (adverse childhood experiences) that a person's childhood has an impact on their chances of triggering natural types of mental illness or addiction.
For me, the most important factor in parenting is that we all make mistakes, every single one of us and many parents out there suffer their own ACEs or their own mental health issues
But blame is different and family disputes or estrangements aren't always due to blame
I think it is only true or right to blame someone in walking away from them if they are the type of person who refuses to be accountable, apologise or make changes to their behaviour for the sake of the relationship.
Some family breakdowns happen without blame, because the other family member is ill or addicted and it was needed to walk away to protect someone's mental or physical health so that they can take care of the people dependant on them.
Which means accountability is different to blame
So many relationships can be saved
I'm a big believer in therapy and counselling for families but it's also possible for those who are able to take that accountability and really talk to actually heal together as a unit and come out stronger in the end