A helpful response:
“We also are men of like passions with you and proclaim the good tidings that you should turn from these vain things (idols) , to a living God, who made the heaven and the earth and the sea and all that is in them. Who in generations gone by suffered all nations to walk in their own ways. And yet He did not leave Himself without witness, in that He did good and gave you from heaven rain and fruitful seasons, filling your hearts with food and gladness.”
This response has some significant detail. I focus on just two.
God has chosen to let the “nations walk in their own ways”. This explains much of the Old Testament history – God was knowable, but humanity chose their own ways without God. This concurs with the teaching in Romans 1 – ‘They chose not to know God , so God gave them up..................’. History is full of times when God interrupts the course of human rebellion, calling people to repent eg Nineveh, but the sad response prevails :- “every man does that which is right in his own eyes”
The second point is that God did give them witness of Himself. He, unlike the idols, is invisible. Yet His power, His handiwork, His wisdom and His kindness can still be seen. This response by Paul, alludes to the ‘fine tuning ‘ of the earth. God designed the seasons and sends the rain to sustain and cheer humanity. Many other things point to the greatness of God eg DNA code, but rain remains a reminder of the kindness God.
Thus the call goes out – “turn from vain things to the Living God.”