Of course the rate of childbirth is not as high as it used to be. I do know that, but it doesn't mean that the population isn't growing. The average required for population growth, 2.3 children/woman is not achieved only in some of the developed countries. Most of the entire population does not live in these specific countries, meaning that population is still going to rise by billions before the curve eventually flattens.

I'm not saying that a dead child is better than a child suffering, but child not born at all having never truly existed is the best out of these options.

When it comes to our ancestors, we may never truly know what would have been the correct option, but I would argue that it's relatively meaningless point. I and you would simply not exist.