Hello ForestGreenCook,
You might want to look at the context of who Paul was speaking to again:
"Paul then stood up in the meeting of the Areopagus and said: “People of Athens! I see that in every way you are very religious. For as I walked around and looked carefully at your objects of worship, I even found an altar with this inscription: TO AN UNKNOWN GOD. So you are ignorant of the very thing you worship—and this is what I am going to proclaim to you."
The fact that the people of Athens had an altar set up "to an unknown God" tells us that Paul was speaking to unbelievers and not to people born of the spirit.
Anyway, regardless of whom it was written to, it is for the benefit of everyone who reads it. All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the servant of God
a may be thoroughly equipped for every good work. The letters to the seven churches in Revelation are good example of this. Though they were were written to those specific churches of that time, they are also directed at every believer to examine himself till this very day and beyond.