> it does more good then harm

This is an oversimplification. If used as a limited last resort it can do more good than harm (which is why e.g. the WHO still recommends using it). DDT is very effective and has certainly saved a lot of lives by preventing malaria infections. But if used carelessly it can do a lot of harm, and various groups of experts who have studied the question have come to the conclusion that its use should be dramatically curtailed, and replaced where possible by other methods of malaria control.

DDT causes fertility problems, birth defects, cancer, etc. to humans, as well as environmental damage.

(Malaria also kills a ton of people, and we should be investing more resources in fighting it, ideally without resorting to heavy DDT use.)

DDT is not known to have reproductive effects or cause cancer in humans. Please do your research and be careful about sources because there is a LOT of misinformation out there.

Here’s Wikipedia: https://en.wikipedia.org/wiki/DDT#Human_health

I am not a medical expert, just passing along what I have read.

Moreover: we know from observation that DDT has severe effects on numerous wildlife species -- some of them intended, many not. It would be highly surprising for humans to be immune to these effects.

Sounds like you did the research care to share your sources for that. Otherwise I'm sticking with my sources that day DDT does cause cancer and birth defects. See Wikipedia article on DDT linked by someone else.