If you compare apples to apples - say my average atheist friend who is a director in a FAANG and also my religious friend who is also a director in the same FAANG.
The former lives by themselves, spends their money on fun things like cars and "toys", etc. Don't get me wrong, wonderful guy (hence friend) but doesn't have those traditional things that historically have been correlated with a fulfilled life.
Meanwhile my religious-FAANG friend has 4 kids, lives in a community where everyone knows each other, lives much closer to family (intentional choice) and just overall sees his life, both the ups and the downs, as part of something purposeful and meaningful.
I would say my religious friend has much more intensity and drama/richness in his life, and maybe no time for "sadness" which I actually think is the right way to go.
I like talking about these 2 guys because outwardly they are apples to apples (same career, similar degree, etc.) but I think this generalizes well to my other friends too. At whatever level of "secular" success and safety, my religious friends just somehow seem more grounded, more belonging in their lives compared to my atheist friends, deal with setbacks better, take a more long-term view and in that traditional sense have more "to live for" than themselves which is very healthy.
America has undergone a VERY rapid secularization. When I came to the US in mid-90s (as an atheist) over half the population attended religious services regularly. Obviously that number is nothing like that today. So what registers to us as an overall change in society (fewer kids, less happy) is actually the proliferation of non religiosity in society and the corresponding magnification of the kind of challenges non-religious folks face.
As a sort of comical but sad example, most my atheist friends "would want kids" but have 30 reasons why it's impossible, between economics, politics, etc. Meanwhile my religious friends just have kids.