Thanks for the kind words. And I don't think you're dooming different timelines. I think there's only one timeline that you continuously recreate until arriving at the timeline where Majora is finally defeated and the curse is lifted. The items you collect that travel back in time with you must have something special about them that allow them to transcend time and space.
If you are
recreating the timeline though, then what happens to the original version of the timeline? Even if the characters from, say, your very first cycle as Deku Link aren't crushed by the moon, the very idea of that timeline being overwritten means the versions of those characters would be erased. The end is the same.
I think the first cycle as Deku Link is the best example of this - think of it this way: In the first cycle you experience, the world of Termina
only has Deku Link in it. The second cycle, however, has human Link. So, then, what happened to the first cycle that ONLY had Deku Link in it? Did it never exist? Surely not, because Link is carrying an item - the Ocarina - FROM that version of Termina.
So either that version of Termina that ONLY had Deku Link in it either
ceased to exist after Link got the Ocarina and travelled back in time (meaning all of the characters were, perhaps mercifully, erased into oblivion), or that Termina was a different branching multiverse that was crushed beneath the moon.
Think of the first cycle from Skull Kid's perspective. He sees a grubby Deku Scrub ascend the tower at midnight. He gets shot with a bubble and drops the Ocarina.
Then what?
He watches Deku Link bust out his pipes and go back in time.
What are the options for what happens to Skull Kid here? He either sees Deku Link disappear before his eyes (the idea I subscribe to), or he (and the world around him) disappears forever and is reborn into the new version of Termina that Link is now in, on the first day.
Because of all this, it seems very likely to me that everyone dies everytime you play the Song of Time.