Cards ERA is over 4. Maddux was overrated.
Not to disprove you, but according to Fangraphs:
Cards (ERA/FIP/xFIP) - 3.64/4.01/3.85
Nats (ERA/FIP/xFIP) - 4.02/3.61/3.38
That says to me the Nats are underperforming and unlucky on homers. As for the more ground ball oriented pitching coach, the Nats are third in K/9 compared to the Cards who are 13th in the majors. 10.85 to 8.61. That just means that it isn't on the pitching coach, it's on the pitchers on how they perform. So to agree with you, Maddux was overrated.