I guess it varies from person to person. I personally wouldn't want D.C. to be just one building and nothing else because then what would be the point of having the setting be D.C.? There'd be nothing to explore if everything was a giant crater. The game would feel empty but not in a good way, in a "there's no point going out there" way I guess.
While I do believe the D.C. we got was a bit too intact, I wouldn't want it damaged to realistic levels either.
I guess they could have made it so most buildings would be a pile of rubble on the surface, but we could explore a lot of underground shelters, compounds, vaults, sewers, underground garages and even metro tunnels (like the cold war era, the USA government build many shelters and compounds underground, people build shelters in their basements, etc. About the metro tunnels it would have to be made more interesting than the ones in Fallout 3 for sure though.).
The problem with that would be it would happen mostly underground and that would deviate from the older Fallouts even more I guess...