The story of Paul’s encounter with the altar at Athens “to an unknown God” is more interesting than most realize: Epimenides was a Cretan whom Paul acknowledges as a prophet who told the Athenians that if they set up an altar to an unknown God, he would save them from the plague they were suffering. In other words, God was still speaking to distant people, even though he was withholding primary knowledge of himself except for through the Jews, and ultimately through Christ.
And we can see this in other places: Balaam was a genuine prophet of God, even though he was also greedy, and not Jewish.
This has fascinating ramifications, and answers one of the main questions many people have about Christianity: what about all of the people who have never heard of it? The answer is that God has still sought to reach them throughout history, and I strongly suspect that his judgement of them is on a weighted scale that perfectly factors in how well the circumstances of their time and place allow. It makes one wonder if the Native American “Great White God” was Yahweh…or similar in so many other cultures…
On a similar note, Simeon’s story in Luke 2 shows that the so-called “silent years” weren’t actually silent. God never stopped speaking to individuals – he just put a pause on big national/biblical level prophecies.