Paul’s letter to the Corinthians was to those within the family, not those outside. He wanted them to be true to who they really are in Christ and not live contrary (1 Corinthians).
One of the things the letter drives home is the fact that the early church was not made up of perfect people.
The other thing is, the problems in the prevailing culture had to be addressed within the body. Sexual immorality, unnecessary litigation, division, eating food sacrificed to idols, marriage, divorce, separation, living single, I could go on and on.
The apostle dealt with the real issues of his day and we must not shy away from the hard questions confronting our faith today.
Remain strong in His Grace.