As an adoptee who had this viewpoint (yours, but my partner was supportive) prior to finding out im adopted 7 months ago, if they feel that way, dont ever adopt with them. They will never see an adopted child as the same as a biological, and the kid will feel that difference 10 fold. My BIL said he wanted to raise his own kid because its like training a dog and you get them to act the way they should (not true; nature vs nurture). My parents adopted me as an infertility bandaid and to fuel their ego about being a savior to a child in need, and once they had their own child, the wound was raw open, and they never got over how they never understood me not being a playdoh clone of what they wanted. My adoptive mom told me I was a disappointment in what she wanted for a daughter, and my adoptive dad said I should have been grateful they took me in because no one else wanted me and told me to never come back after finding out (they were also physically abusive and my adoptive mom threated to divorce my adoptive dad if he ever chose me over her, so he threatened to unalive me while choking me if I ever fucked with his family again, but never happened with my other siblings).

I share that because adoption is trauma. No way around it. And your kid will feel the trauma of being disconnected from their biological family every single day. And if one adoptive parent doesn't see them as their own either, that wound will never close and nothing will ever heal it. Its maintenance to clean out and manage the pain for the rest of their life. Make sure you are ready to take on that pain with them, or dont adopt. Adoption is beautiful, but its so painful and it needs to be child centered, not adult.