People who were teens during WW2 would not have known these things. In their era people more often than not died before retirement. Many people had no pension. Most people did not go to college so they would only dream that someday they or their kids would. With their parents having lived through the Great Depression neither housing nor food were guaranteed. The time you’re thinking of is well past the war during the late 50s and 60s and even they had to deal with the threat of nuclear war and actual wars like Korea and Vietnam and yet they didn’t lose hope.

Social media can be blamed in the sense of giving people too much choice / competition and such, but yes, the key problem is people trying to tackle this from an angle which seeks to invalidate people's feelings rather than look if things are heading into the wrong direction.

Yes, war sucks. Famine sucks. All of that sucks and can make people just as hopeless. The premise is the same as the one now: people don't feel in power of their own future, incapable of getting what they want. A large crowd will immediately retaliate "but your demands are too high!" Really, most people's desires would've been considered pretty normal a few decades ago. Their parents and grandparents had an active role instilling those desires into them.

Here's a mental exercise for people. Imagine the following guarantees: A partner who won't leave you as long as you keep your stuff together and will actively support you (and expects the same in return, obviously). A home where you could raise a kid, maybe two, each with a separate, small bed room, a separate kitchen and a living + dining room combo. An average career (average salary, nothing too glorious). Life up to 75 and a retirement by age 60. You can fill in the specifics however you want. Most people in their 20s would be just fine having such a life.

The above used to be pretty easily attainable as long as you put in some effort before. Now, the above feels unattainable to a large degree of young adults. Even the ones who did exactly what their parents told them to, are noticeably ahead of their peers in terms of academics and career, and still struggle to get what their parents were able to at the bottom of the ladder, let alone what their gen X / boomer equivalent had. Teenagers are learning these things through both the news and the internet, and want none of it.