how should I as a person in late 20s deal with the fear that every piece of evidence suggests my generation (and subsequent ones) will be totally screwed in the future
Consider that late-teenagers and 20-somethings successfully "dealt with the fear" of the Great War, the Great Depression, WW2, the Cold War incl the Cuban Missile Crisis and others, assorted oil crises, acid rain, holes in the ozone layer, Chernobyl, more economic crashes in the 70s, 80s, 90s, 2000's... And every time, the world didn't end, and most of them lived to a ripe old age and life itself generally improved. I get that the things on your list seem terrifying but that's because it's the first time you've seen anything, in a few years you'll look back and realise that there's always some ongoing "end of the world" panic and when it doesn't happen, they'll dream up another one, either to sell you something or trick you into voting for them.
Consider that late-teenagers and 20-somethings successfully "dealt with the fear" of the Great War, the Great Depression, WW2, the Cold War incl the Cuban Missile Crisis and others, assorted oil crises, acid rain, holes in the ozone layer, Chernobyl, more economic crashes in the 70s, 80s, 90s, 2000's... And every time, the world didn't end, and most of them lived to a ripe old age and life itself generally improved. I get that the things on your list seem terrifying but that's because it's the first time you've seen anything, in a few years you'll look back and realise that there's always some ongoing "end of the world" panic and when it doesn't happen, they'll dream up another one, either to sell you something or trick you into voting for them.