In DC, as in San Francisco, the trains are more for commuters to get into and out of the city. They're not really for connecting within or outside of the city. The NY area is better about that. (But not great.)
If I ever moved back to the area, I would seriously consider Bethesda. Easy access to DC, and a neat town in its own right.
Every city has outlying suburbs and not a single one has excellent transit throughout the entire metropolitan area. The DC metropolitan area has the lowest mode share for private automobiles and the highest mode share for public transportation of any except for NYC. It is objectively the second best city in the US for getting around without a car. It is clearly not as good as NYC but it is certainly not worse than San Francisco.