Social Security should be Opt-Out if the taxpayer chooses.
Opting out will remove the ability to receive SS benefits at a later age after what has already been withdrawn from the taxpayer has been returned, plus interest.
Those who choose to stay in SS have the ability to do so.
Some background/reasoning:
SS was created to protect (mostly) elderly against economic insecurity. The combination of a longer lifespan (due to medical improvement /innovation) and increase in overall job loss (due to the Industrial Revolution) led to more people without a job for a longer period. SS was created to provide an income for individuals in this group. Savings/investments (especially tax-advantaged retirement accounts) were not something the average American had back in the 1930s.
These days, an individual can create free and easy investment accounts and do it all themselves. An additional 6.2% of one’s paycheck going to tax-advantaged accounts that gain dividends and market value for their lifespan will, on average, far exceed the value earned simply from US Treasury interest.