John, I agree with many of your observations. Most certainly, Lutherans deserve a shout-out for their status as poster child of declining U.S. church attendance. From the start, they suffer one huge, additional hurdle when compared to, say, Catholic churches – no substantial immigration of believers from the faith’s roots (Germany and Scandinavia).
Even as a pre-teen, I would sit in the pews of our family's Missouri Synod church (the conservative Lutherans!) and observe the tiny number of parents with children, and all the seniors, and wonder how long that particular church would survive. As it turned out, they owned enough land, in a desirable section of the city, to ensure their existence for decades – regardless of attendance and operating income, aka offerings and estate gifts. (And let's tax these, while we're at it.)
With respect, I would tend to disagree with an earlier poster's comment about U.S. organized religion sustaining its numbers going forward because people tend to "find God" as they age, become infirm, etc. This may have held some weight in past generations, but I feel that today's young and middle-aged people moving to non-belief have done so because they've given it long-term, considered thought; have access to a far greater array of relevant discourse in media, both pro and con; experience less societal "stigma"; and in general, are less likely to revert.
If I'm ever on a burning plane as the last engine explodes. I do reserve the right to have whatever religious conversion comes to mind.