Materially people nowadays are far better off (on average). There were severe shortages of housing after WW2, worse than now. Most people then didn't have central heating, indoor bathrooms, washing machines, certainly no tv and mod cons like many people have now. Only the most recent generation (aged maybe 40-60) really had it good growing up.
Some people now are poor, but I reckon they are not the only ones feeling miserable so don't really prove anything. Even this so called poverty is a far cry from the days when babies got abandoned on the streets and old people went into the workhouse.
People haven't grown up dealing with hardship and worry as they did in former generations. Instead they have parents who try to make them happy and provide for their wants. They therefore lack resilience and are unable to deal with failure, disappointment and imperfection in life. It's human nature to worry about something and if you don't worry about immediate things such as getting enough to eat or your parents smacking you if you misbehave, you then start to worry about other things such as your appearance or what pension you will have in 50 years time.
A fundamental mistake is in thinking the problem is due to poverty/lack of money/lack of opportunity. We have more money and opportunity than ever. 100 years ago people had virtually no choice about most aspects of their lives. It's to do with appreciating what you have, enjoying human relationships and taking the time to do what's important (for children this includes lots of time playing without adult interference, preferably outside).
So many families nowadays have 2 working parents and think they need this to earn enough to live. Yet if people were willing to accept a more basic lifestyle they could easily live off one wage (outside London at least).
If parents became less materialistic I think children would be happier too