> Why not something like cloud seeding with sulfates?

Same reason we don’t reach for surgery every time anything in our body hurts: we want a least intrusive (for the planet) method rather than crazy ideas that we don’t know the consequence of. We know very well what happens when people use less carbon, there are plenty of countries on the world right now who are doing that. But no, if it’s not out of sci-fi it doesn’t tickle your fancy enough to try.