I first used the DC Metro when I was 9 back in 1994. At the time, it was the gold standard of mass transit. It was A LOT more cleaner and high-tech than the decrepit and rat-infested subway in my hometown of NYC. Over the years, however, it has declined in quality. Management has become apathetic in the maintenance of the system. Many unqualified people are running the system. In addition, they focused more on extending lines then maintaining the existing lines. There's nothing wrong with adding more stations, but you can't just ignore the existing infrastructure.
There was a devastating crash on the Red Line in June 2009. 9 people were killed. The crash occurred because a computer operated signal system malfunctioned and failed to alert the operator of a train that there was another train ahead. There were several other incidents, including a train decoupling in between stations, and an electrical fire that caused a passenger to suffocate. And to make matters worse, the system used to be safe. Now, people are getting stabbed, shot at, and robbed in the parking lots.
A major flaw in the DC Metro is that on all of the lines, there's only 1 track in each direction, meaning that if maintenance needs to be performed then an entire line has to shut down, rather than to use the second track.
As a former DC Metro enthusiast, seeing the Metro gradually decline is so painful.