The antinatalist might argue that, though historically this may have been the case
Historically, approximately half of children died before the age of 5.
But I also don't think it's fair to compare modern reproduction with historical, because the contexts are very different. For starters, it is more of a conscious choice now due to modern contraceptives.
Secondly, modern society (at least in developed nations) tend to place a significant value on human life. Look at how things like medicine and safety have improved over the past 100 years, and of course the huge drop in child mortality rates. There is much more consideration given to individual well-being. There is of course another angle to look at: maximizing joy vs minimizing suffering. Positive utilitarianism vs negative utilitarianism. Antinatalism clearly focuses on the latter.
I get a chuckle out of this. It isn't the threat that they think it is.