enclave and supermutants are fallout, sure you can take em away and call it a fallout game, but the enemies in new vegas don't stack up, powdergangers and ceasers legion etc are not really very effective from a players point of view, they're boring to fight and no supermutants hardly at all in new vegas? i hear everyone saying how civilized new vegas is, well at some point the game isn't really post apocalyptic anymore, it won't really be classic fallout, but yeah you can make a game about a civilized world where you live in a nice town and go to college etc and call it fallout. but if the game world gets too "civilized" it kinda loses the whole point of the franchise. bethesda will get back to basics with FO4. they do a much better job at representing a post apocalyptic world than obsidian does.
Again, you're arguing that "Fallout" isn't Fallout. Its a bit like saying that Octopus' Garden isn't a Beatles song because neither Lennon or McCarney wrote it, nor did either sing lead vocals.
Go and play "Fallout" (Not "Fallout 3", not "Fallout: New Vegas" but "Fallout"), count all of the NPCs that are in the Enclave and come back and try and make the same argument whilst keeping a straight face.
For Fallout to truly "Get back to basics" as you suggest, there would have to be no Enclave, just have the pre-war civilisation hinted at in computer files only - noone claiming to be the heirs to the old world at all. (Not even the Brotherhood claimed to be that, although they did claim to be its guardians)
As for your comment on a post apocolyptic world, Obsidian weren't trying to portray a post apocolyptic world. You can't fail at something you weren't trying to do.
They were trying to portray a post-post-apocolyptic world, That which happened after the things that happened following the end of the world. If anything, Bethesda failed when they tried to say that Fallout 3 was 200 years after the bomb - After 200 years there should have been governments, or at least proto-governments; In Fallout 3 things kinda froze 5-10 years after the bombs dropped.