First off, lemme congratulate you for being the very rare and elusive self-aware fan who happens to be a boy(that is a workaround!). This is anything other than an insult- you called yourself a Fallout elitist. This actually makes your opinions more valid in my eyes because you aren't operating under some sort of false perception that you are entirely fair. With that in mind, I hope to address several of your points in this post:
1- Earlier, you said that NV is 400% more of a Fallout game than FO3, but only 15% of what the sequel should have been. You also, being aware, said that it was ten years of hype and reading/re-reading the Van Buren design documents that created the benchmark. Well, the issue is that the game design document for any given game is always insanely better than the final product. Even if Van Buren were made, it would probably only be half of what you expect.
3- It is very likely that DC had some sort of missile defense, considering it was a vital cornerstone in the nation's lifeline. The sheer volume of targets likely overwhelmed the system, but the lack of such a defense in LA is likely what lead to total destruction in one city and not so much(by comparison) in another.
1. True, but it isn't just about the design documents, Fallout was never about sandbox exploration, annoying radios, dumbed down RPG mechanics, FPP format or "not" having a map node system for me. A lot of other variables reached my conclusion that New Vegas is more like a glorified demo of what a real sequel should be like.
But yeah I know, concept art for example always look... Just... It just looks so [censored] awesome! Then the game comes out and one's like "meh" about it.
Still, even if Van Buren wasn't an exact replica of it's design documents it would have been a Fallout game and not an Oblivion game disguised as Fallout. (I know it's harsh but New Vegas, while improved heavily, is still in core Oblivion.)
3. That could work, except, I find no evidence that they had such a anti-nuke security system.
One can always speculate on what happened and give several great, believable and functioning reasons for it as well.
But Fallout 3 was Bethesda's first go at it, in Fallout 4 on the other hand, they will have no excuses, they should know Fallout by then.
Oh and I'm not a boy.
[edit]
I got it!
Since there was an oil crisis cause of the resource wars, most of china's missiles ran out of fuel before they reached DC! (While a joke this could actually work.)