Growing up facing an increase of the likelihood of multiple doomsday scenarios being highly promoted nonstop, from global warming and climate change to gun violence to the rise of authoritarianism and throw in a Pandemic, has to drag on their generational happiness. Not to mention more than some question regarding America's ability or appetite to remain a superpower, the attack on individual rights and highly polarized politics.
I can't think of a shittier time to grow up in America than maybe the Silent generation preceeding the "greatest generation." But even they enjoyed the roaring 20's before the Depression and between wars. Maybe you'd have to go back to the civil war to find a young generation who had it tougher? Sure they enjoy the fruits of a modern, technologically advanced society, but there are significant mental and emotional stressors that can't be easy for young minds to deal with in a healthy way. Seems to me like the bad really outweighs the good for that generation. They likely have a lot of hopelessness.