I believe narcissism and hedonistic desire is likely relatively constant across generations. What differs is the technology each generation is raised in and has access to. I believe (opinion, I'd like to see studies about it actually) that the easy access to the narcissism reinforcing tech Gen-Z grew up with has made the expression of these desires more pronounced, and not at all in a positive way.
Personally, I've seen it in action (of course, this is anecdata, now, so not necessarily generalizable). I know a 20-something guy and am involved in his and his friends' lives to a certain extent. These young adults haven't had adversity much different from anything I faced growing up in the 80s with a deeply impoverished family living in the south, or that my wife faced when she was growing up in the same era, but they are far less resilient (in almost every aspect) and tend to treat every little setback as a major trauma. I'd say the outliers of my generation (in terms of emotional instability and lack of resilience) have become the norm in Gen-Z, and I hypothesize it is due largely to the prevalence of modern social media and how it facilitates and encourages this extreme-drama view.
The economic situation of young Americans has significantly declined over time. Failure to recognize that as, hard stop, the most important factor, means your perspective is way off.