I often wonder about this, and here’s my (u/dys)topian vision:

The top 5% of children in some measure of ideal traits for just ruling are whisked away to a bubble where they are educated for the purpose of governing, with no opportunity to ever rejoin the general populace. They have absolute power but no opportunity to benefit themselves or their families.

That or we could tax externalities globally.

Socialism, ie a system whereby resources are allocated according to some sort of public good as opposed to mere expansion of capital

Are you suggesting that in practice under a socialist system corruption doesn't take place, or just in theory?

I'm saying a small number of people amassing a large amount of wealth through exploitation of the labor of others for personal gain is not what drives a socialist economy. Corruption and exploitation exists in all societies, but in capitalism it is a necessary element for the function to survive. There is no non-exploitative, fair capitalism.

Is there non-explotative, fair socialism?

Redistributing a shrinking pie. Sounds like a great plan.