The dinosaurs became extinct because they didn't have a space program.
I'd repair our education system or replace it with something that works.
SF isn't a genre; SF is the matrix in which genres are embedded, and because the SF field is never going in any one direction at any one time, there is hardly a way to cut it off.
We should not have assumed that a political space station could be built.
Anything beats an expensive stack of paper.
I'd visit the near future, close enough that someone might want to talk to Larry Niven and can figure out the language; distant enough to get me decent medical techniques and a ticket to the Moon.
We need to take command of the solar system to gain that wealth, and to escape the sea of paper our government is becoming, and for some decent chance of stopping a Dinosaur Killer asteroid.
As for AIDS, it's a plague. We are human, we get plagues. They come along every so often, kill off two thirds of the population; in the next generation it's a quarter; after that it's a childhood disease.
I'm not predicting; I just love playing with superconductors.