I used to be the same, but I think I understand now what the flaw in my logic was. Your parents are bad parents, and thus, they are selfish. I believe that "successful parenting" is the exception to when this is selfish. If good men can be born, then is birth the evil, or is it something else?
1. The child is almost certain to face adversity:
This is true, but adversity is only bad subjectively. If you can raise a virtuous child, one who is unflinching in the face of adversity, then what you have done constitutes successful parenting. You may be inundated by a fusillade of hardships, but it is possible to face them with equanimity, so that internally, you are unaffected by them. What I mean is this. You cannot avoid life, but you can avoid interpreting life negatively. Even when losing a friend, there is still an underlying beauty in that chaos, there is a sweetness in the tears you shed over a lost friend because they are tears of love.
2. Humans cause pollution:
This is true, but it's also true that a well nurtured, intelligent, dedicated human can do a great deal to reverse that pollution (see: Elon Musk, solar power, green planet initiatives, etc...). It is not that we have too many people that is causing the global climate problem. It is that there are too many stupid people, too many worker drones, too many slaves that incessantly consume and pollute, too many selfish, evil, bad people. People who were not raised by loving parents, people who were not raised by intelligent parents, capable parents, etc...
3. My parents had me, and I turned out a social outcast loser, etc etc...:
It's possible to change who you are. There are multifarious books and podcasts on psychology and parenting that you can understand how to treat a child to be a well rounded, good, individual. Someone that people actually like. If you make a good person, then you are doing good, because the world can always benefit from more good people.
