How does this answer suit the simple son’s question?

The simple son is not stupid. Rather, like the wicked son’s wickedness, the simple son’s simplicity is a character defect. He is simplistic and superficial because he is haughty. With the redemption long past, he arrogantly asks, “What is this?” That is, “Why dwell on the past?”

We address the simple son’s conceit by recalling our humble beginnings as slaves to the mightiest nation in the world. We also note that G-d’s strong hand rendered this nation powerless. Thus, we disprove his notion of human supremacy and prove his disdain misplaced.

haggadah Section: -- Four Children
Source: Sefas Emes Haggadah