Wow you have a lot of followers. I had to think carefully whether to take the time to replyi to this, as now my reply will probably not be seen, but your article struck a chord, so here goes:
I don't recognise this curve at all, it does not fit with my own personal experence.
Life for me (about twenty years older than you), has been something more or less continuously improving, with the odd wobble due to diivorce and death of loved ones.
To me it looks like folk my age and maybe a little older (Boomers), had a distinctly different experience of life from folk your age (Millenials?).
I have a cousin your age, with whom I have every sympathy, he aspires to have the same as folk my age, and the age of his parents, but has no chance, the goalposts keep moving, every time he reaches out to grab the prize for working supremely hard (Probably harder than I ever did), the prize gets snatched away by ever rising house prices, cost of living, in short, inflation.
The truth is that it is becoming impossible to remain solvent, even by owning and running businesses, miillennials appear to be taking the brunt of burnout, they are closest to the moving target, so they put in the most effort to try to achieve it, but the constant disappointment takes its toll, I think.
To me this is the real reason you feel as you do, and the studies you mention, seem a kind of distraction, maybe designed to try to hold the system together from falling apart, as it is doing, for a very solid reason, which I write about a lot, it is all about energy, and where we get it from.
I would recommend looking at who funded the research, what was their motive for funding it, and did they study a balanced spread of ages, or concentrate mostly on your age group?
Anyhow, I don't think the answer to feeling better is to take seriously research trying to encourage you to just double down "You'll feel better soon".
To me, there are folk who are identifying something much deeper, something spiritually missing, a lack which has always been there, but now is being felt much more acutely, now that the sweetener of financial success is being removed, we have to look further than where we've been looking previously for happiness, it actually isn't about money, though that has helped in the past, now this spiritual lack is becoming something really affecting the happiness of a lot of people.
I've written about how energy, and the way we deal with it using money, is at the root of the problem.
Essentially, energy is becoming ever scarcer to us, but we need abundance of energy to be happy, energy is what we thrive on, and create value from. If we are not able to do that, then of course we will be unhappy.
We have reached the point where we should be questioning how much futher down this road of unsustainably destroying Earth for energy that we wish to travel, and I present an alternative, which seems to be being forced on us by nature, using the silver bullet of inflation.
My analyses are technical, but take into account things like stakehloder analyses, which go into what drives people, and what are the systemic consequences, so it can be dry reading. But if you are interested, you can find by looking in my profitle.
Meantime, for those more oriented on feelings, as I guess you are, being driven to write your article, I think this writer below puts his finger on it, and imho is much better therapy than studies designed to just make us "Double down":
https://medium.com/@davidprice-26453/creativity-and-the-outbreath-c27c2b07ab4c
