It's clear that most people are happy to be alive. So even if you personally don't like being alive, having children is moral.
I can imagine a world where having children wouldn't be moral. It would be a world in which most people hated being alive. We don't appear to live in that world.
I want no such thing, merely offering my differing point of view here. It probably doesn't have relevance or any sort of impact in the lives of most people, but claiming that having children is universally moral could be challenged at the very least.
If nothing else, each child is another mouth to feed and will contribute to the carbon footprint of our species. While the planet could sustain more people on it, in our current climate of consumerism, i personally don't believe that the world needs to strive towards overpopulation and accelerated exhaustion of the resources that we have (amongst other things).
Personally, after often experiencing such existential dread and finding that it impacts my life in a pretty negative way, i've largely switched over to the nihilism school of thought. Then, it can be argued that bringing children into this world just to doom them to a similar fate would be pretty immoral.