Today, as an average, children are healthier, more likely to have food they need, will be exposed to less crime, have more protections, they're living in an age of more social acceptance, less likely to die in combat (sure, there are always wars, but this is an era of relative peace- over the last several decades globally wars are declining).
That is great. Wonderful even; however, kids today have no path to making a living for themselves.
In the past, I would teach my son how to hunt and gather food. Today, all I can do is send him off to school and hope that he will find a job afterwards. The thinking is, "Nobody owes you a job", which is ultimately true, but then you straitjacketed my son and do not allow him to hunt and gather. How then is he supposed eat?
No. The ENTIRE reason modern society is such a terrible place to bring children into is because all of the resources are owned. Naturally, owned by someone else. The only way for my son to live is to either accept that his life depends on the whims of someone who owns the resources (slavery with or without chains) or take those resources from the putative owners. The entire situation is a LOT more complex than this simplistic narrative but then we get into "regulations and corruption" when trying to take those resources legally.
So yeah, you are 100% correct that many of the less important, but still extremely important, things are MUCH better nowadays. What you are missing is that the single most important thing, the ability to survive on their own, has been taken.
Tell me again how it is a good idea to bring children into this world.