I will say, talking about gay adoption, a child should have a mother-figure and a father-figure, but not necessarily a mother and father. Does that make sense?
It's good that you're okay with same sex couples adopting, although a lot of kids don't have mother or father figures and they turn out just as good as any other kid.
All that matters is that the kid grows up in a loving environment and that the parent(s) do their job as a caretaker.
I think what chakun is getting at is that a "traditional" mother and father fulfill very different roles. It's possible to switch roles and/or have one person be both, but it's good to have exposure to both.
As someone who grew up with then without a dad, I can say that I really never needed one. My mom did a hell of a job by herself, fulfilling both roles, and I don't necessarily think that you need both in the first place. Personally I think I'm better off and it's made me a more independent person.
All that matters is that the kid grows up in a loving environment and that the parent(s) do their job as a caretaker.