re: Not only that,...
A lot of post-Golden Age* SF examines the ethics of whether or not a thing that can be done should be. That's probably easily traceable to what we grew up calling The Bomb, but the thinking has applied to many major tech developments.
And there's plenty of non-optimistic SF out there, and has been for decades. Dystopian SF goes back at least as far as Well's The Time Machine, runs through 1984, Earth Abides and The Handmaid's Tale, and includes the Cyberpunks. Phillip K. Dick wasn't exactly what I'd call an optimist, either... and as near as I can tell, more of his stories have been adapted to screenplays than any other SF author, by a wide margin.
[* - old SF truism: "The Golden Age of Science Fiction is 12"]