> This prolonged interim state results in a lot of pain, and some studies suggest today’s young people are suffering more than previous generations did.
These kids aren't being drafted into war service. Crime and teenage pregnancy are down, civil rights are increasing, commodities are cheap and plentiful, access to global information and communication is higher than ever, advances in medicine continue to make formerly terminal diseases become manageable or preventable. The biggest thing millennials have to stress over is their debt and their ability to secure a job, both of which are issues most people have had to deal with by their late 20s.
From what I understand of the quarter-life crisis, it presents mainly in people who have been so privileged that they feel that even though they can self-sustain, they should be doing something better, like following a passion, or living in a different place. Fear of death is another factor, but it's less present than the fear of missing out.
Your late 20s are basically the end of what should be a wonderful time: wasting your youth and not worrying about your body falling apart (which it will begin to shortly). If kids these days are actually in a great deal of pain, it's because our society has given then an irrational sense of entitlement and fear of not having the best of everything.