Just chanced on your post and am moved to comment as I was a 'late talker'. My parents tell me I had few words (I was a 3rd child so they had prior experience) until sometime after I was three and instead mostly relied on nonverbal communication (gesture, pointing, facial expressions etc). Then over the course of maybe a month or two developed normal speech and began asking incessant questions. I also followed this pattern with reading and other intellectual skills as an older child and adult, though this may be coincidental.
Now, 60 years later I have been married for decades, have grown kids and live comfortably because I am paid well to exercise judgement (not law). However, my wife also differs from the norm and my kids certainly do (Two have had 'diagnoses' tossed their way). That may be a consequence of assortative mating but it has also meant that two of them have got themselves a great deal of scholarship money at Uni.
Selection of embryos based on polygenic scoring is a cute idea but is decades away at best.
Your ability to pick an appropriate partner to conceive a child with has been honed over 100,000's of years (actually, more like 'since sexual reproduction began'). However, it's far from perfect and there are some gross genetic failings (existing and de novo) that genetic screening can recognise that aren't obvious at the everyday scale of day to day living.