Growing your own baby is different than just taking one to raise. If someone who wants to have their own baby should be expected to care and love another one, why not say the same for childless people?
Both just don’t want to adopt. You can’t force the same feelings to happen for a stranger child as you would your own, even if that would be nicer. Not for everyone at least.
As a marmite lover, I’d give it a shot.