Olivine beaches: unknown impact of this mineral in large quantities on local life, plankton, general ocean life. Since ocean life is a major component of climate (through the vast amount of carbon sequestered), this could have unpredictable consequences. Probably one of the less crazy options.
Sulfur dioxide in the upper atmosphere: unknown impact on ozone layer. Unknown possible chemistry in high radiation environment. Unknown effect on weather patterns. Unknown chance to fall back down to earth. Reductions of incoming solar radiation have unknown effects on all ecosystems on the planet. Extremely dangerous to try.
Shade satellites: similar concerns as above, except for ozone layer, chemical reactions, risk of raining down. Production of the huge number of satellites needed to matter has risky environmental costs. Huge number of objects in orbit will greatly accelerate orbital collisions, may destroy the constellation before it has any real effect.
The risks are currently inestimable, while the risk of 2.7C is at least understood.
On the other hand, reducing carbon emissions is doable, and has little risk of negatively impacting the environment. It's the right solution, and any time wasted by delaying it with promises of Geoengineering is criminal.