it's not any kids. Oh no. It is their kids, their genetic offspring. That is selfish.
Adopted kids is more similar to caring for a pet or plant so another living being with which you do not share that many genes. However, still a hobby in the sense of unnecessary, elective activity.
All I can say is, it's best you don't have any kids.
I bet adoptive kids beg to differ with your viewpoint and are grateful some folks decided to take an elective.

