Read it all. The whole piece as well as the links and comments are well worth the time. Of all the bits, I found this most revealing. If you look through the Christian Century article you see this quote:
[James B. Lemler, Episcopal director of mission] also said that officials were heartened that average Sunday attendance in 2005 did not decline as it did in the previous two years. The average Sunday worship attendance in 2005 was 787,000 people, down only 8,500.
Since that time, according to the most recent data available (from 2017) ASA has declined to 556,744, a decline of more than 29%.