[dragonwriter]

> This sentiment is grossly nauseating, to me. Having children is not an achievement.

The GP didn't say “having children”, so even to the extent one agrees with this claim it's a non-sequitur.

> If your greatest contribution to the world is birthing a child, you have failed as a person.

Perhaps. Certainly, if that's your greatest contribution to your child, you've done very little as a parent. But when people say that someone's greatest achievement is their children, they probably don't mean giving just giving birth to (or fathering) them.