Great post! My mom grew up in DC, and when I was younger we'd often go back to visit her family that stayed in the area (I grew up in CT). Lotta fond memories on the Metro, it was so exciting to ride as a kid... You're right though, it's a clean, well-run, and easy-to-navigate system. WMATA's done a great job with it!
Compared to NYC it has always been "clean." But it has shown some decline in recent years.
Maybe it was experiencing it through innocent eyes that made it so enthralling... either way seems like it's improving at the very least!