I’ve only been to D.C. once, and was very impressed with how they changed the traffic to all go one way at rush hours.
I didn’t see any slums (stayed with a friend) - and it was all very beautiful.
It was a different story in the ‘60s and ‘70s.
My great Aunt moved from there to Arizona before the riots, (LBJ administration).
Parts of the city (vicinity of 14th and K) have, to my understanding, still not recovered, although that may have changed since I was last there.
Stay close to the Mall and in the upscale part and it is fairly nice—for a city, that is.