In no way would I call ss a Ponzi scheme.
A Ponzi scheme involves fraud and money being secretly spent from the funds received. The madoff Ponzi scheme was a classic Ponzi setup....investors paid money in, and madoff gave them a fake statement showing a great rate of return, when he had already spent the principal.
I have paid into ss for 35 years, and I started getting my monthly payments last year. The amount I get is exactly what was forecasted by ss.
Ss is well funded, and in the future there will need to be some minor adjustments to continue that.....but ss will be there. There is too much political damage that would occur to Congress if they tried to end ss or to defund it.
If you set aside the same percentage of your pay that would have gone to ss, you will get a better rate of return than ss would give you.....but are you setting retirement dollars aside? Most people would fail to put the 7.65% aside and save it for retirement....you may be the exception.