This post at Aeon may go a little too far, but there's some truth in it: A lot of times, the characteristics that are ascribed to a generation don't really apply well to the people in that generation -- or they apply at some times in life but not others. In which case they are probably more descriptive of a time in life than they are of some kind of generational cohort.
I recall that in the mid to late 1990s, "Gen-X'ers" were seen as disaffected slackers. There was something to that, but since a generation is usually taken to span about 20 years, it didn't apply across the board. I was a Gen-X'er, but from the earliest end of that time frame and didn't have all that much in common with the alienated goofball of Reality Bites. But on the other hand, the alienated goofball represented real people as well. Some of their alienation remained as they aged, but not all, and truth to tell, disaffection is not uncommon to late teens and early 20-somethings.
Major events can affect large groups of people -- World War II made the generation that fought it something it never would have been otherwise. Other events can affect a wide range of people, but not as deeply. People my age take note of things like the murder of John Lennon, the attempted assassination of Ronald Reagan and the explosion of the space shuttle Challenger, and we will probably always remember them and what we felt when we learned of them. But I can't see how even the three of those added together could have the same kind of impact brought on by the most massive conflict in humam history.
Plus, a lot of the research into generational characteristics focuses on Western or developed nations, and often only on the U.S. What a Rwandan teen saw in the 1990s probably worked on them a little differently than, say, the death of Kurt Cobain did on American kids.
I often work with college students, young adults and youth, and I try to keep abreast of the kinds of things written about them. Some of them ring true, but some of them don't. The Aeon writer has some points about how a significant amount of the stuff I read oversells the ideas of generational characteristics and differences, but there's some baby in that bathwater and I can't buy the suggestion it's time to toss them out completely. But I would make sure there's some salt handy.