>The Millennials were largely spared from the carnage because all but the last few years of them were beyond puberty when the phone-based childhood swept in.

Every generation thinks its suffering is unique and worse than those before it. Read Douglas Coupland's early 90s novels (Generation X and Microserfs) to see how Gen X fared in contrast to their parents. Watch Eden of the East to see how middle-Millenials struggled with the rising concept of the NEET (in Japan, the US, and western Europe alike) as our Gen X and Baby Boomer parents couldn't understand the difference in economic and life circumstances between being 23 in 1980 and being 23 in 2008.

Smartphones and social media are accelerating the decline, but there's evidence collected over the past ~60 years that points to a trend of diminishing quality of life. A great non-fiction economics-oriented book on the US version of this is The Rise and Fall of American Growth: The U.S. Standard of Living since the Civil War by Robert Gordon. (https://press.princeton.edu/books/hardcover/9780691147727/th...)