If you put 6.2% (12.4% total with employer contribution) of your income away into index funds that grew at 7% per year, at $100k/yr gross salary ($12.4k/yr) from ages 25 - 65 (40 years), you would end up with $2.6m (in today's dollars).
$2.6m converted into dividend funds with a 3% yield would be $6.6k/mo.
I don't know anybody getting $6.6k/mo from Social Security...