The Legend of Zelda: In Defense of Fi

gamerant.com:

While The Legend of Zelda has featured plenty of characters accompanying Link on his adventure, from Ezlo to Midna, The Legend of Zelda: Skyward Sword draws the most contention. Though the game may divide fans, most would agree that Fi, the spirit residing within the Master Sword, is a frustrating character. Symptomatic of a time when games were criticized for holding players' hands, Fi's constant interruptions to direct the player or provide hints made her a target of ire.

However, The Legend of Zelda: Skyward Sword represented a huge effort to establish a significant portion of Zelda lore, providing a starting point to the story that has been ongoing across many games in its series. Fi is arguably just another part of that strategy, an attempt by Nintendo to provide some backstory and characterization to an otherwise inanimate object: the Master Sword. For a game that sees players revisiting previous levels often, ensuring the player knows what to do and where to go is essential.

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Though Nintendo may not have set out to establish an overarching narrative centered around Link and his adventures, that's exactly what it achieved across many subsequent games. The series has secured itself a legacy that will continue for decades to come, but with that comes an expectation that such an influential series would have a grand origin. While Link and Zelda were straightforward to establish and Ganon was given an origin with Demise, the Master Sword and its manfestiation likewise needed an origin.

A mystical sword merely imbued with great power from the goddess Hylia comes across as lackluster given its significance and constant need to be wielded by Link.