The world is in a weird place..

[Squall of SeeD]

I can't think of any other instance where a spell's visuals are used metaphorically, the things you described about the spell just enforce how immensely lame the spell actually is.

Sadly, yes.

Since at the climax of the spell the game clearly says "Earth" as a caption and shows your characters being scolded by the suns outer layer upon it, this spell DOES suggest that the planet is called Earth.

Yes, I meant to edit that sentence -- and then forgot -- to say the game's dialogue doesn't refer to the Planet as Earth like Final Fantasy IV's dialogue did with its Planet:

(Spoilers of Final Fantasy IV; don't highlight it unless you've played the game, or if you do so, do so at your own risk.)

(SPOILER)Cecil: ...Who are you?

Old Man: I am FuSoYa, guardian of the Lunarians.

Rosa: Lunarians?

FuSoYa: In eons past, a planet between Mars and Jupiter verged on
extinction. The survivors escaped by ship to the blue planet.

Cecil: The blue planet...? Our home?

FuSoYa: Yes, Earth. But because the people of Earth were still
evolving, the survivors created another moon, where they now sleep.

Edge: So these survivors became Lunarians, and they're still sleeping.

Sorry about that.

There is no way around how uninspired and thoughtless the implementation of this spell into Safer Sephiroth's aresonal was.

Agreed. Especially in light of the title "Gaia" having now been given to it.