PC - i agree its a complex issue
Adoptive families often break down when the adoptees are adolescents. They are far more likely than bio children to have serious mental health problems, learning difficulties, addictions, personality disorders or get involved in crime.
So when an adoption disrupts or an adoptive family breaks down, its not that the parents are " giving back" the child/ren. Its usually that the young people concerned have to go into residential care or hospital to have their needs met better. Sometimes they are placed in secure units because they have committed serious offences or are a risk to themselves or others.
You will not read of these cases in the tabloids as they are ( quite rightly) protected by privacy laws.
I know many families who have faced such a terrible situation - to realise that they can no longer safely provide the care that their child needs. Parents and other siblings have been attacked, assaulted with offensive weapons, had bleach thrown at them etc. Younger children have been sexually assaulted, pets have been tortured or even killed. Parents have to make a terrible decision to protect themselves and their families
i don't think any of these tragic families would describe themselves as having " given back their child". As Nina says, many marriages do not survive this kind of trauma , most parents are siblings carry the sense of guilt and failure for the rest of their lives.