I'm not OP of that post, but can elaborate.
Adoption is a fantastic solution for kids who would otherwise be brought up in care, and particularly for those whose parents are unable to give them a stable upbringing because of their own problems, e.g. addiction.
It's not a great solution for infertile couples desperate to have their own child. Sometimes the parents' emotional expectations are not fulfilled, and very often the child will not be wholeheartedly accepted by other family members. The child is likely to notice, and that's a significant burden on mental health while growing up. Some degree of attachment disorder is fairly common.
There are also ethical considerations when adopting from overseas. Even in the UK, back in the 1960s when I was born, there was considerable social pressure on unmarried mothers to give up their babies to more "deserving" married parents – often with a devastating impact on the birth mothers' mental health.