I have a childhood friend who literally refers to everything as a Ponzi scheme, much of it is out of humor. However, very much really is.
Anything that has the "greater fool" theory at work is essentially a Ponzi scheme. Take the stock market. You need someone to pay a higher price than you did to make money, greater fool.
I have been involved in markets for years and in the end I know it's a zero sum game. I make money when someone else is the greater fool. Sad, but reality.
I am not sure I can agree completely with the zero sum theory since capital keeps increasing all the time. But, you are spot on with this
Many people have trouble getting this. Especially those who haven't traded or hadn't had the opportunity to have a business of their own. If one works for salary they are pretty much blind to what really goes on around them.
In a zero sum game, why would the value of the SPX increase over time and not be stagnant?