No, not really splitting hairs, as the solution for each is consequently is going to consequently be different. Ponzi schemes get banned because they are a form of fraud and have little redeeming value. The solution to a Ponzi scheme is to shut it down and arrest the con artist.

Social Security and other pay-as-you-go schemes aim to reduce poverty, especially elderly poverty. By this measure, it has succeeded quite well (http://www.nber.org/bah/summer04/w10466.html), and the probable reason pay as you go was chosen I imagine was to provide immediate benefit (recall this scheme was launched during the Great Depression). I would consider it radical (and would want one to provide considerable justification) if one wanted to ditch Social Security entirely.

A better debate in my mind, of course, would be whether to phase Social Security into a fully funded model versus pay-as-you-go model. I can buy that kind of argument, a fully funded retirement scheme is more secure than a PAYGO type.

But even as it stands, the current Social Security gap doesn't sound like a complete disaster. Part of it actually is because Social Security is not completely pay as you go -- Congress raised payroll taxes in 1983 in part to cover this gap (http://www.pewresearch.org/fact-tank/2015/08/18/5-facts-abou...). Part of it is because we have some variables to play with -- raising the retirement age or raising the payroll tax cap, for instance. Medicare actually sounds like its in worse shape at this moment.