This speech is held up as a great example of contextualizing the message of Christ. Many who make much of adapting the message to fit the listeners miss Acts 17:16, "He was greatly upset in his spirit." That is the starting point for pluralistic engagement. Anything else is self-indulgent.
He spoke at their invitation and started the best place he could discern, the unknown God. He talked about a God they didn't know and called them to repentance. He contrasted the Living God with idols and ascribed breathtaking sovereignty to Him, down' to the very places and times in which we live. He spoke of judgment and the resurrection, but not explicitly about Jesus.
That must be why the response was joining Paul, not believing. He had not yet given them enough information. They had to hang around to get to Jesus.
The crowd had each of three possible responses: Some mocked him. Some needed to hear more. Some joined him and believed.