Is it selfish to choose not to have kids?

The 'future taxpayer' argument deserves a closer look, because it's morally grotesque in a way nobody acknowledges. It says: create a human being so that the human being can fund my retirement. That's instrumentalization, pure and simple: treating a person as a means to an economic end. Kant had a word for what's wrong with that, and it's the foundation of modern ethics. If your case for having children is that we need workers, then you have conceded that children are inputs, and inputs don't obligate anyone. You can't argue in the same breath that kids are precious ends-in-themselves and also that we need a fresh supply of them for the pension system.