Money from your check DOES go to your future benefits - the value is accrued and logged. But yes, the money you pay goes to current retirees.

Soicial Security can be fixed, but there are political reasons for not doing so.

As you said, Republicans want to privatize it. Also, if everyone had a robust Social Security pension to retire with, many would leave the workforce and deplete the pool of desparate workers. The pool would then have more clout to raise wages, organize and demand better working conditions. Keeping SS on a failure razor edge benefits corporations and businesses