There is a tone in this thread from a few people that looking to history for insight and inspiration is not valuable. To me, that attitude is another indicator of why Western culture has stagnated.
We do need to look back. We can't move forward without a clear idea of what we want and where we'd like to go, and that is entirely based on where we (personally and collectively) came from. This is true for every generation.
Anyway, I've observed my peer group to be unusually nostalgic for their age (we should still be in our "prime", not yearning for the past already!). Yet, I still understand it, because I'm that way as well.
To me, it is because my generation completely lacks any vision for the future. There are no ideas, no leadership, no clear set of goals besides aspiring to what our parents and even grandparents had. We are stuck because we believed hook, line and sinker that following all their rules and advice would benefit our future, and then it didn't.
The boomers did a lot of interesting things when they were young. They brought new ideas to the table, experimented, rebelled, tried to bring their ideals into reality. A lot of their experiments didn't work out, and they later set into the conservative lifestyle of their parents. The majority of them had children later in life (judging by the size of Gen X cohort vs. millennial, and their time periods), and so many millennials today have boomer parents who taught them not to take risks or try to change things but to follow the rules out of dire fear of harm; taught them that sex is dangerous, taught that interacting with other people is dangerous, taught them to stay inside and seek passive entertainment instead of going out into that "scary world", taught them that the only path to a decent living and respect within society was through the education system (indoctrination), ensured they'd live outside their means under the boomer assumption of continuous prosperity and wealth, extended their childhoods as much as possible and yet expected independence and instant success, and then started to blame them as being entitled brats when the economy tanked and they weren't able overcome it immediately, clinging instead to their parent's keep-your-head-down principle or making feeble protests with no alternative vision to draw from.
There was a very short period, at least in my childhood, where I was free to roam - that was in the mid 1980's and early 1990's. I tend to be nostalgic for that period. Sometimes for the entertainment of the time, but more so the atmosphere and belief that I could live and breathe as a free person, and everyone else around me could, too.
That is the root of my nostalgia, and I suspect it is for many others, too. It isn't the "freedom from adulthood", as the many short-sighted millennials seem to attribute (I really, really despise the word "adulting" and want it to go away as soon as possible), it is the freedom to act within society in a way that we believed was possible when we were very young (hehe, Milne). We feel we have very few opportunities now, are constantly under surveillance, and have experienced so much of our lives vicariously through media, that if we do climb out of our hole it will be a great feat.
I do think generation Z will have a revival from the oppression of the older generations, similar to the roaring twenties.
I suppose there is a difference when a group of millennial friends pull out the Nintendo and play Duck Hunt instead of merely commenting on a Facebook post with a screenshot of Duck Hunt accompanied by a snappy caption. Reliving the moment is much more authentic and deplorable than recognizing it briefly, isn't it?