That sounds really fucked up. Yeah, I think one main argument about antinatalism that hasn't been addressed enough is how people can never be qualified enough to be parents. This argument might sound similar to "you will never find the right person, only the one that's good enough", but being a parent holds way more responsibility and the potential cost of bad parenting is immeasurable. Unfortunately, there's seems to be studies suggesting parents have very little influence on their children, at least less than we think (Bryan Caplan wrote a book about it). And not enough influential people had published books about how parents cause tremendous pain and suffering to their children, those books just won't sell well I guess.
There’s not much evidence that we can instill values into our kids. Personalities are strongly heritable and not subject to much change from the environment. Short of not traumatizing kids and giving them a fundamentally safe environment with decent nutrition (itself not a trivial achievement), a lot of what we do as parents has little effect. Not that it stops me or anyone else from trying.
See, e.g., Selfish Reasons to Have More Kids: Why Being a Great Parent is Less Work and More Fun Than You Think https://www.amazon.com/dp/0465028616/ref=cm_sw_r_cp_api_i_gYS.CbW2QJ4GT
Caplan's "Selfish Reasons to Have More Kids" (https://www.amazon.com/Selfish-Reasons-Have-More-Kids/dp/046...) has some data showing that parents are putting more and more time into children. (And his argument is that it is mostly unnecessary, i.e. it doesn't correspond to improved outcomes for children, given a relatively normal stable family.) I wonder how much of this is just changed social expectations (e.g. call Police / Child Services if you see a kid walking home along from school), how much is social signaling, how much is reduced family support.
Do you mean ROI for the parent (satisfaction of spending time with your child) or for the child? It seems counter-intuitive but I believe a lot of research has shown that upbringing actually doesn't matter too much, provided you meet a certain obvious threshold (giving them proper food, not abusing them, etc)