Sure, "gone" is clearly hyperbole. But the sentiment is accurate. GenX will pay for the Boomers to get 100% of their SS while they will likely receive less than the full value of their SS.
How long so you think you can charge an individual or company an "extra 100M"? Realistically would you stay in a country that suddenly added an extra 100M to your tax bill?
And your numbers are wealth, not income.
Also, there are ~600 billionaires in the US, most of them however would pay $100M tax (and realistically numbers can be adjusted down by stretching over say 100k highest TC individuals rather than 11k like my original statement).
[0] - https://www.fool.com/retirement/2018/10/28/americans-average...
Let me put it in another way. I think a 60 year old doing manual labor in 1980s would be less productive than a 72 year old doing desk work in 2030.