Honestly, the optimism/pessimism common in fictional is a decade thing more than anything else. Every medium seems to go through periods of negative, dark story

Honestly, the optimism/pessimism common in fictional is a decade thing more than anything else. Every medium seems to go through periods of negative, dark storytelling and positive, upbeat storytelling alike, usually flipping once people are sick of how saturated the previous style has become. Go back through TV history and note how stuff like Star Trek and Doctor Who flips between being dark and upbeat every decade or so. Or how comic books went through a cheery silver age before a depressing dark age and a more upbeat modern one. And yes obviously there's a cultural aspect too. Compare something like Doctor Who's reboot to Black Mirror; you can tell which one started in 2005 and which one started in 2011 by the tone of the whole affair. Still, it'll come to pass eventually. Optimistic sci-fi fiction will come back in vogue soon enough, especially when people start getting sick of the 'everything and everyone is doomed' tone that much of today's fiction seems to have.