I can say I'm thankful for the WW trait as it means I never have to take it or see any of the silliness that comes with it. As for the roots, or origins of Fallout I think you're referring mostly to FO2. FO1 was a much darker game than its sequel and I feel took itself much more seriously. FO1 is my favorite of the two chiefly because I couldn't stand all the pop culture references and breaking of the 4th wall and so on that happens in FO2 that kept pulling me out of the experience (not to mention the ridiculousness of talking, sentient deathclaws, and an unavoidable, single outcome boss fight, but that's another thread)
As for hardcoe mode I can say it is def my favorite way to play, so much so that I cannot even play FO3 anymore without it. Too each their own and all that
Fallout 1 is my favorite of the series to date. The 4th wall is meaningless to me, as I never play an RPG as though I were the PC, (and was ~for all intents, substituting for them in their own world and adventure. That's just not what I look or in an RPG.
IMO Fallout had a fantastic setting and overarching theme ~ with much of it lost in one degree or another from game to game ever since. Fallout ~taken deadpan seriously as some sort of survivalist chore... is (would be), about the most depressing computer product that I can imagine; but taken in the context set by the original team, its a masterwork of manipulative interactive fiction. Its a harsh gritty, amoral environment set in an idealized future gone wrong, amidst a surreal expanse of totally unknown wasteland brought about by global nuclear war.
And the weird happenings in the waste may be real on some level or not, and the jabs at the player serve (quite well) to lighten their mood. Fallout is a near perfect mix done right (but almost assuredly not quite done as intended; and with a few lucky mistakes and coincidence.. that just worked in the game's favor).
Fallout 2 started losing this 'magic' from the start (IMO), but was still a masterwork of it's own.
Fallout 3 was a labor of love by the artists, and yet lacked the heart of the originals [IMO]; this isn't really fair, because the only way to have gotten that would have been to hire a few of the original devs [IMO]. Even so... FO3 though fantastic in the art & design area, seemed [to me] to be derived from a cursory glance at the series, and full of misconceptions by the development leads.
I suspect that New Vegas was an "Our way, or the highway" sort of affair. Everything that I dislike in it (excepting the bugs) was inherited from FO3; and curiously, I did not like the 3d assets as well as FO3's ~It shows where the studio strengths are most developed.