Income disparity has become a huge problem in America and it is getting worse. However the answer isn't about the rich throwing dollar bills out the window but rather returning to paying their fair share as they did during the greatest economic growth period in the country's history; a time when those marginal rates were sometimes as high as 91%.
Alexandria Ocasio-Cortez's proposal is hardly revolutionary: increase marginal rates for every dollar above 10 million. This money will then get fed back into the public infrastructure development, schools, health and other beneficiaries. Your entire society benefits a little and the wealthy can still lead the lifestyle they desire. During Eisenhower's presidency those marginal rates kicked in above $200,000 which is roughly equivalent to $1.7 million today and far more aggressive than Ms. Cortez's proposal. During that time prosperity was extremely high and a healthy middle class was built as a result.
Some point to current stock and job market health but they are not indicators of the problem because being employed doesn't mean you are prospering and many of these people are not market investors. Hence, you can forget these as metrics for a nation's overall health. You can also forget about the myth of trickle down economics.
If the current system were working so well we wouldn't be seeing fully employed people living out of their cars struggling to pay basic needs and foregoing health care payments while some people swim in their billions. We also wouldn't be seeing the US rank so low in the overall happiness rating (18th) for such a large industrialized nation losing to more social democratic countries like the European Nordic states, Australia and Canada.
Clearly, oligarchy works very well for the few but not so much for the majority.