Well the root problem is of course money, as always. We are already producing enough to feed everyone on earth for example.

True.

But since number must go up, the metric for rich assholes isn’t actually productivity or needs being met, but growth.

I don’t think you can simply decouple productivity and growth.

For decades and decades we have automated more and more and yet work has not become less. Where do you think this surplus of value, created by automation and additional work by the working class ended up?

Partially to the rich but partially (a maybe too small part, I agree) to the workers, to pay for all the new things we have in our life. We don’t live like our parents or our grandparents honestly.

I don’t want to just “tax the rich”, that is merely the first step.

As long as the tax is proportional and not something like “you are a billionaire, so we will grab everything over 1.000.000 a year” I agree, else you will end up with nothing.
And not because billionaires will flee the country but because nobody will care to go over the 1.000.000/year (or whatever limit you decide)

The goal has to be abolishing a system which not only allows for this concentration of wealth but is designed to do so.

To replace it with what ? I honestly don’t see a better system actually.