More folks my age believe that Aliens are regularly visiting the Earth than believe that they will collect any meaningful amount of money from Social Security. In this estimate, I believe they are correct despite my low probability estimate of regular visitation from interstellar illegal aliens.
Social Security is not structured as a forced savings/investment program, but rather much like a tax-supported welfare program with a loose connection in amounts paid out versus amounts paid in. Relatively recently outflow exceeded SS taxes collected. Some speak of a 'Social Security Trust Fund', but frankly, that is merely an accounting fiction. Where is the trust fund? Why, it is in fact just part of the national debt. You didn't really think they did something like used it to buy tons of gold and oil did you, cached somewhere in the deep Midwest? Or invested it into a Sovereign wealth fund like the Chinese? No, they used it to offset deficits and reduce their apparent size. Anyone who talks about a Social Security 'lock box' with an eye to mollifying you ought to be locked in a box.
But, be that as it may, SS would still be in deep trouble even if it were structured the way some people still naively assume it is----like a gigantic 401k system with conservative investment management. Even under ideal conditions, there will be massively correlated net selling activity as the huge elephant in the demographic python enters retirement age--i.e. the Baby Boom Generation. And what does massive net selling activity generally do to the prices that the sellers receive?
At bottom, money or investments represent a present claim to resources in the future. A society can only support X% of its population not being productive. In crude terms, only so many can ride in the wagon that the rest must push. The increase of the retiree to non-retiree ratio means problems, big problems, in the fairly near term future and massive headwinds for the economy as a whole. In addition, the lower 'demographic quality' of the younger generation will not help either---anyone with delusions that illegal immigrants and massive legal immigration from the 3rd world is going to solve this problem should sell the excellent drugs they have discovered to fund their own retirement.
There is, however, a fairly time-tested strategy for retirement, used for most of human history. Raise functional children, preferably several of them, and hope that at least one of them and their spouse will look after you in your declining years. For reactionaries I'd suggest at least 3, four if you had the good sense to marry early.