Robbing Peter to pay Paul isn't sustainable [1], but that's what social security is. Social security is not a guaranteed solution. If we have to raise taxes or collect additional taxes, that makes it a ponzi scheme. Cutting benefits is similar: you either lose the money now or later.
Discussion forums such as this are one of our few hopes for generating s sustainable solution. Just because a solution doesn't currently exist doesn't mean we should be complacent with how things are.
[1]: http://money.cnn.com/2016/06/22/pf/social-security-medicare/