Bab. Talmud Pesachim 116a says that during the Seder, one begins with shame / humility and ends with praise. Meaning, that during the Magid section of the Seder, we begin with the "mood" of our humble history as slaves in Egypt, and end with praising G-d for our Exodus and Redemption.
The Mishnah states that we use the section from Deuteronomy 26.5 beginning with the words ארמי אובד אבי
If the mitzvah on Pesach night is just to tell the story of the Exodus, why do we need any "theme" at all? What do the concepts of humility vs. praise have to do with telling the story of the Exodus?
If this theme is important or critical, aren't there other sections in the Torah that might accomplish the same job? (See next question, as an example)
The mitzvah is to tell the story of the Exodus. The section the Mishnah suggests seems like a round-about way to do this. ("Round-about in the method that we do it in the Haggadah. We recite verses then explain this by using proofs from other verses, the majority which are in Exodus. Why not just read those Exodus verses directly?) Why not read selected verses that talk about the 10 plagues (We do a bit of that in Maggid, anyway) from parshat Va'era and Bo, and perhaps some verses about the commandments of matzah and marror (like we recite in the Rabban Gamli'el part) and, maybe end with some verses surrounding the story of the Splitting of the Sea (more than the 1 or 2 verses that we recite related to Rav Akiva's sayings. etc.)?
1: ולפי דעתו של בן אביו מלמדו. מתחיל בגנות ומסיים בשבח. ודורש מ״ארמי אובד אבי״, עד שיגמור כל הפרשה כולה. And according to the intelligence and the ability of the son, his father teaches him about the Exodus. When teaching his son about the Exodus. He begins with the Jewish people’s disgrace and concludes with their glory. And he expounds from the passage: “An Aramean tried to destroy my father” (Deuteronomy 26:5), the declaration one recites when presenting his first fruits at the Temple, until he concludes explaining the entire section.