Well, we could all move into a matrix-like universe where we’re gods, I guess. Then all we’d need for civilisation is server farms and the infrastructure to maintain them.
More near-term, if I was dictator for a day I’d impose a wealth cap between at maybe 10 or 15 million CAD and a guaranteed income you can live a very basic but comfortable life on. I feel like that would solve most problems. This could be applied globally too (with some ramp-up time) if we’re assuming world government. Climate change could be addressed with a carbon tax high enough to fund the offsetting of the pollution’s social cost.
I’m a wonk and I could go on, but those are the biggest things.