Ultimately it comes down to this simple fact:
Each individual will have to answer on judgement day for their own person actions and inaction. So to the individual, it is IRRELEVANT what priest, pastor, scholar or pope says. It is the individual who will decide what they will accept and follow. Thus, the defacto authority for interpretation is the individual, not the community or church.
But those shepherds, and there are many, who deliberately mislead their sheep will also have to answer for their actions.