To reframe your point: maybe we should be careful to identify where the baby is and spend a little less attention on what billionaires want.
What percentage does that equal on the lower end? You say it does not justify messing with the system, but what is that based on? What would you feel is an equitable distribution of wealth within a country?
https://ourworldindata.org/grapher/average-real-gdp-per-capi...
Day-by-day the world is zero sum.
There are definite improvements (a fair amount of medical science), but I'm not sure on balance that the planetary destruction/extinctions/etc outweigh them. So, using made up GDP/capita numbers for justification that the world is "improving" is tenuous.
So don't compare the worse case subsistence farmer, with what was middle class in the US a few decades ago, where suburban houses on a couple acres were affordable my the top 70% of the population. We have more trinkets, but the price of basic necessities are becoming more "expensive" every day.
The middle class in the US a few decades ago lived pretty good lives, but were very much dependent on market economies and innovation for their standard of living.