Almost no baby is adopted from birth. Babies removed at birth can usually only be fostered until a judge makes a placement order allowing them to be placed for adoption.
Sometimes, those children may be placed with foster parents who are also intended as adoptive parents, subject to final court outcomes, which does improve continuity for the child if they go on to adopt, but which carries its own particular demands of parents.
So to answer your question, a parent adopting a child needs to be able to:
(a) manage often very significant health uncertainties - the baby is more likely to have had a difficult birth or suffered a birth injury, more likely to be born to parents with genetic disorders which may or may not be inherited, more likely to have had a concealed pregnancy which meant proper medical care wasn't provided during pregnancy. For many of these, the impacts may not be known for several years. A parent adopting a very young baby needs to be able to live with the uncertainty, and then needs to be able to parent whatever needs emerge because of these factors.
(b) parent a child that has often experienced significant in utero trauma - this could include exposure to drugs and alcohol, exposure to domestic violence, or persistent heightened stress and anxiety with attendant changes in cortisol levels by virtue of being carried by a mother whose circumstances almost certainly cause significant stress.
(c) manage the role of an often extended birth family in their child's life - managing contact, sometimes written and sometimes in person - with siblings, half siblings, grandparents and birth parents. Sometimes, this can come with safety and security concerns where a birth family is known to be violent or to be intent on tracking down the child. Being able to manage that in a way that does not instil shame or fear in a child, and lets them explore and understand their life story is extremely difficult.
(d) if you're talking about placement for birth, then the parents also need to be able to parent as foster parents for potentially up to a year before they can be matched for adoption. This means always holding in the back of the mind the potential that the child may not be adopted and may be removed. It means facilitating contact with birth parents. It means trying to balance building a bond and attachment with the child with the potential of them being removed hovering over you.
Are you starting to see why comparing surrogacy to adoption is so wide of the mark yet?