Why should any one person get to decide? Right now we have given the power over that decision to the worst people.
I think a good first step is to recognise when someone has the power to incentivise behaviour and see whether they are using that power to incentivise negative behaviour. This is currently the case with most of the powerful institutions in our capitalist society. We do not live in a world of scarce resources. In most places there is more than enough food to go around, more than enough housing for everyone to be housed. We are forced into "survival mode" by the fact that wealthy people and institutions are hoarding resources and preventing access to them so that they can exploit us for profit.
If we simply checked and limited the power of such institutions, allowing people the freedom to act in a less competitive manner, we would probably have more co-operation and a more ethical society. We've seen plenty of examples of this before.
What about the basic social animal instinct of co-operation and empathy?
This is why people who sacrifice their lives for others are exceptions rather than norm. Seeing somebody lying on tracks in front of an oncoming train, the common instinct of onlookers is not to jump but stay where they are.
Sometimes reformulated as "An it harm none, do as ye list."
A suicidal person can say "I don't want other people to save me from dying therefore I will not stop others from dying."
A rich person can say "I do not want charity from others therefore I will not give charity to others."
Who gets to decide what is "Good" and "Ethical" behavior ?
What exactly would be the "incentive" "Good" and "Ethical" behavior. ? You say that capitalism can be dismantled in favor of another form cooperation that directly incentivizes helping your fellow human survive. Is this not in direct contradiction the base animal instinct of self survival. The incentive would have to be huge in order to override this base instinct.
You suggest Golden Rule as sufficient way to define "good behavior". But Golden Rule itself has shortcomings and criticism (https://en.wikipedia.org/wiki/Golden_Rule#Criticism). Do you have any sufficient argument against these criticism.