The point of Demise is that he is Ganondorf’s precursor. His hatred is so strong that it is rebirthed cyclically in the form of Ganondorf throughout the other zelda games. This is meant to explain the origin of Ganon as an evil character.
My question: what is the point of showing a precursor to Ganon, if the precursor is even less interesting than Ganondorf ever was?
If they wanted to explain the origin of evil in the zelda franchise, they should have written a story that shows how it came to be, write a story that shows HOW a man became corrupted so badly that he started the ganon cycle. Or maybe it had something to do with the tribe that created majora’s mask. There are lots of ways to take it.
Instead, they just said “ganon is evil bc he inherited it from some other, less interesting, equally evil guy. ……don’t worry about why HE was evil because we aren’t gonna explain it”
Demise’s curse is no different from what we already saw at the end of Ocarina of time: https://youtu.be/ge8zd1ZR-hc?t=56
I’d also add that SS also doesn’t actually show the origin of the master sword. You start the game by finding the “goddess sword” which already has Fi in it and is clearly already blessed. All you do is power it up, just like you did in the wind waker.