There are indeed "statistical averages", otherwise we all would have to wear custom tailored clothes.

But yes, the "blank canvas" concept we see promoted in Poserdom simply does not work if you want true realism.
You can't simply mix and match morphs to "dial a human" and expect realistic results.
There are rules, and some of them are very subtle.
Even the best real world artists work with live models, and we expect hobbyists to turn a stylized Barbie doll into a real human with just a few dial spins ?

So the best way to achive a convincing result is to slavishly copy an actual human without "adding" or "sanitizing" things here and there.
Forget about "artistic vision" and simply concentrate on the craft.
Just copy the shape you see, that's all.
And don't eyeball, Use a photo reference and stick to it.
Yes, it's boring, but it's the only way to get a solid foundation.

Even if the shape chosen is not everybody's dream woman, most people will at least subconsciously notice the "realness" over a figure that was build by a committee.

This was done for MIKI, and that's why she is such a convincing figure.
Because every little detail is "right".
(Except for the fact that she is quite tall (!) for a japanese woman because her body was sculpted after 5'5" (1,65m) czech model Aneta Keys.Lol.)

She failed for other reasons, but the sculpting and her ecpression morphs blew everything out of the water DAZ had ever produced. (And still does)