Am I just a grognard, or are Dragonborn and, to a lesser degree, Tieflings universally despised?
I can't answer the first, but you're wrong about the second, pretty clearly.
Both seem more "kewl" than "cool", more post-2000 World of Warcraft-esque fantasy than classic Lord of the Rings fantasy or New Wave Talislanta-esque weird fantasy.
This is some weird, stupid pejorative stuff going on here. What on Earth is wrong with Wizards of the Coast publishing an edition of
Dungeons & Dragons informed by
modern fantasy ideas instead of just the traditional Tolkienesque crap or the Eighties' version of "modern"?
Talislanta is
twenty-one years old, dude. It predates Second Edition
AD&D by a few years!
But I guess I'm just a bit surprised they are both core; now I was out of gaming from about 2003-08, but it seems they kind of came out of nowhere in terms of centrality to the D&D ethos.
"Ethos" is a meaningless term as you use it here. Did you mean "mythos"?
In any case, they didn't come out of nowhere. Wizards of the Coast has previously stated that any book they publish with "dragon" in the title sells noticeably more than other books, so obviously dragon-related things are popular with the playerbase; likewise, it's pretty clear that tieflings have been popular player races since Planescape came out in 1994, so at this point - even if they are different in Fourth Edition than they were then - they've got a reasonably long history in
D&D.
More to the point,
D&D has to stay current. More and more players are coming to the hobby whose first ideas about fantasy aren't restricted to
The Lord of the Rings, and it's a terrible idea for the game to offer them nothing other than the most staid and traditional fantasy ideas because it
won't work to attract them. Even the highly successful films jazzed the damn story up with acrobatic action sequences inspired more by modern expectations than a desire to stay true to the tone Tolkien would have envisaged.