The "problem" is that it's all comparative, even if in absolute terms you are right - life is undeniably better than it used to be by every metric.
But to give you an example - my grandma had 8 siblings, out of which only 4 survived into adulthood. They mostly died before even turning 1, the typical "one day he was fine, the next day he turned purple and died, the nearest doctor was 2 hours away if your neighbour let you borrow a horse cart, so that's just what it was" case. Her father and her uncle were taken into Auschwitz and miraculously returned but never wanted to talk about the horrors they have seen while there. For the rest of her life she endured living under communism, seeing her peers in other countries have access to riches she could only dream of.
So now when you talk to her, how can you blame her for thinking that kids nowadays are spoiled, if they have everything provided for them, they have never experienced physical violence of any kind, but they are all depressed and sad about life being shit and saying how it was better in the good old days.
Like, from her perspective, it's impossible to understand.
But also, from the kids perspectives nowadays, all they know is a world where the "old" people have houses, jobs, stable incomes, and they cannot even hope for any of it. 50 year mortgages, 700 job applications with no interview, social media blasting images of a life that they know they can't ever have.....of course they are depressed. Just showing them stats that say "you live better, comfier, safer andd healthier lives than pretty much anyone else ever in the history of humanity" is not going to help if all they know is how much "worse" they have it than the people who came before them.