Only one episode to go in my (mostly re)watch, I'm afraid. The K/S is pretty much on par with TOS, and it has some beautiful lines like:
McCoy: (After an encounter with an advanced alien who turned out to have visited Earth and passed as a god for various civilization, something that happened so often I have to assume they all sort of stepped on each others' toes): Spock, I wouldn't suppose that Vulcan has legends like those.
Spock: Not legends, Doctor. Fact. Vulcan was visited by alien beings. They left much wiser.
That's on par with Worf's "Our gods are dead. Ancient Klingon warriors slew them a millennia ago. They were more trouble than they were worth."
Humans... Well, if we go by the myths, we mostly had sex with them, and/or used them as figureheads in our own politics and self-destructive wars. I love the "humans are the Doc Browns of the Quadrant" fanon, but even before we confused the Vulcans by building a warp engine out of scraps (and then doing the very first initial testing in space
, piloted by the lead scientist/engineer
), ancient godlike aliens probably talked about humans as being (a) much likelier to have sex with you than most other species, (b) apparently good listeners if you seemed omnipotent enough, but in the back of their little but twisty minds constantly trying to figure out how to use your literally otherworldly knowledge to increase their social standing in their pitiful societies, or, yes, get laid.
Centuries later, why do you think (Watsonianly speaking) there are half-human descendants of almost every humanoid species in the Quadrant? B'elanna is half-Klingon, Deanna is half-Betazoid, Spock of course is half-Vulcan, and I'm pretty sure there are others, often with cultural or political implications. Both Spock and Deanna belong to hugely influential families in their societies, and although Worf's is a slightly different situation — Klingon parents, human foster parents — the former were of course pretty much as elite as you can get in the Empire. Add Janeway's somewhat, er, forceful adoption of Seven, and even Data's situation, and you get a picture of humans not just (or maybe necessarily) friendly in the sense of "we don't fight other species just because they are different", but rather with the systematic habit of sleeping with or adopting anybody who looks close enough to humanoid.
I'm aware of the Doylean reasons that might make this the result of sampling bias, but there's a case to be made that, as exaggerated as Kirk's reputation might be (and as exaggerated as Riker's self-image might be), humans as a species have a long, pre-warp history of sexual xenophilia; maybe something specific to the species, maybe a side effect of the multiple "gods" that hit on us during our formative years as a pre-planetary culture. In any case, it could be an underrated factor in the shape and spread of the Federation.
(I've seen the "WARNING: humans will mate with anything" graphics in Tumblr, but it'd be hilarious if "down for weird sex" were the humans' equivalent of Vulcan logic or Klingon fighting as a species-defining particular skill.)
PS: What about Sarek? I don't think he was *strategic* in his family building — he canonically loved Amanda, Spock, Michael, and, I assume, Sybok &mdahs; but I have to wonder if he might not have concluded or suspected that the strong strain in Vulcan society for cultural and biological isolation would eventually be counterproductive and should therefore be somehow made more flexible. Not something the Vulcan society at large was prepared to consider, and not perhaps something he was ready to argue for, but if, as I said, it wasn't the reason
why he married Amanda and adopted Michael, perhaps it's an argument that made it possible
, specially the former. I don't think Sarek would've married and have a child with Amanda, regardless of his (Vulcan face: ughhhhhh) feelings for her, if he thought it would be harmful to Vulcan society.