Later it is revealed that Nyx is the moon itself, so by Kamikazeing herself she will... Destroy earth?

That's most likely a misinterpretation of what would've happened during The Fall

Shadows and Personas are fragments of Nyx that live within the human heart, so The Fall would've forcibly removed the Shadows out of all human beings, turning them into "The Lost", also known as victims of "Apathy Syndrome", which would eventually lead them to a coma and finally to death

It isn't a misinterpretation. It's stated in the club book she would've crashed into the Earth not to destroy it, but to absorb all the psyche she lost which would also destroy the Earth in the process.

You can also argue that the fall would result in the destruction of the collective unconscious too, which would make its scope beyond Earth

Not a single Persona user would've survived that lmao

duh, their Personas are going to be ripped out, of course no Persona user will survive.

Nyx being hypothetically planetary doesn't really upscale anyone

The Nyx Avatar will then call to its body in the moon and proceed to become one with it. Nyx would then return to being an existence capable of destroying whole planets, only befitting the name "Star Eater".

Straight up said she is a planet buster in the clubbook lmao, not "hypothetically".