dont get too worked up about not haing the pentagon city site. you probably wont be able to see those things unless you are really high up anyway. you could probably only see the monument. you wouldnt be able to see the capitol unless you are in the uppdeck along third base. the capitol is really far from pentagon city. you probably wont see the lincoln memorial, because it is low.
the location they chose is fine. lots of close metro stops and lines. so you'll only be able to see the capitol from right field. it will be much better than the view from pentagon city in left field, but it is much closer. i think the more downtown location makes for a much better game day experience, especially if they can pull of the waterfront development and revitalize the area around the stadium