Why doesn’t the Passover Seder focus more on the positive aspects of being a free people and less on the negative aspects of the story?

Why isn’t Passover a massively happy celebration? The Seder plate isn’t that positive (shank bone, horseradish, salt water) For comparison, Juneteenth in the US focuses on the end of slavery not on what it was like to be a slave. Daily Show on Passover.