If genetics/parental upbringing had very little to do with child outcomes then the entire concept of parenting would be irrelevant.
You could just choose any partner, have a child, leave them to fend for themselves on the street, it'd all be down to random chance and then suddenly 50% of those kids end up in the 50th percentile or above academically, financially, whatever metric you choose.
I would intuitively need an incredibly, incredibly strong proof to show the opposite were true, on par with someone telling me that in their city gravity runs backwards or something.