Quote - Add to the mix palms of hands, soles of feet, how much sun some areas get vs. how much others get and you wind up with a whole mixed bag.

That's really tricky, because most of what we think of as "realism" is generally from photos rather than life.  Most of the photos and film we see are of people with quite a lot of make up.  Most of the media we look at are highly post produced.  I've done images with Blackhearted textures that looked odd to me because he made his textures so realistic that the outside of the arms were very red and darker, while the inside was much paler and less red.  That's quite natural for an outdoors, atheletic person, but can look unusually uneven in a render.

At the end of the day, you have to make your own judgement about what looks right.  Once you do, don't be afraid to edit textures you own to look like what you want.  Just don't save over the originals and don't redistribute them.  If you use Photoshop, adjustment layers can give you a non-destructive transformation that you can copy to other maps.  You can use other textures, flood fills, and seamless skin patterns as overlays, and then use masks to non-destructively vary their effect.   All of those are easy to copy to other documents, so that you can make your textures consistent across UV maps.  If you paint corrections or changes on top, just avoid the seams and you'll be fine.

As for real world ethnicity being a complex issue, I considered that a given and beside the point of this thread.   There are tons of realistic characters of visibly European heritage.  The ones that are supposed to visibly show any other type of heritage are often much less realistic, IMHO and (based on the original post) the opinion of the OP.

I've seen many characters that get darker tones inhumanly wrong to my eyes (wrong hue and saturation, like I said).  I've seen many with burned in artifacts that make them problematic with my materials.   Even in lighter shades, there are certain skin types and hues I've found difficult to obtain.  Just considering different types of textures, there are huge gaps in my library that I've deliberately sought to fill, and been unable to.   All of those types are particular to non-European ethnicities.