Everytime I look at small problems or big global problems, if you follow the money trail, it all leads to some billionaire who is either working towards increasing their wealth or protecting their wealth from decreasing.
Everything from politics, climate change, workers rights, democratic government, technology, land rights, human rights can all be rendered down to people fighting another group of people who defend the rights of a billionaire to keep their wealth or to expand their control.
If humanity got rid of or outlawed the notion of any one individual owning far too much money than they could ever possibly spend in a lifetime, we could free up so much wealth and energy to do other things like save ourselves from climate change.
I think you two are speaking about different steps in this hypothetical transition. You are talking about the long term goal, the other person was talking about the transition from now to the long term scenario. There is very real danger that the power vacuum left by the x-billionaires could be gobbled up by a small group of people. This cannot be dismissed even if we all agree on the end goal.
Secondary critique, set the wealth cap in relation to some other moving metric. I think a multiple of minimum wage would be great, give incentive for the wealthy to increase minimum wage to achieve a higher cap.