You need to correct behaviors and find out the underlying reasons WHY they are doing the things.
Except that parents have plenty of incentive not to find out, because it's their responsibility and probably their fault.
That only increases the urgency of finding out, if the person is really serious about being a parent. Children are supposed to have a life that's better than ours was; they are not supposed to inherit severe character flaws because we were too cowardly to deal with them.
I do agree, though, that there are lots of self-centered (and often emotionally immature) people who really do fit the description you gave. That something might be uncomfortable, or require some effort, or *gasp* involve admitting that they were wrong and need to change, these things are enough to stop such people from doing the right thing no matter how important it may be, no matter how lasting the consequences are. It's even harder to raise a child and help them become an adult when the parent is not really an adult themselves.