Even the Final Fantasy 7 Rebirth explainer book can't explain what's up with the JRPG's divisive ending

gamesradar.com:

If you're hoping Final Fantasy 7 Rebirth's new grandiose Ultimania novel provides answers or hints regarding the ending's lingering mystery, you may be disappointed. 

Before we continue, take this as your chance to peace out if you haven't finished Final Fantasy 7 Rebirth yet, as we're entering spoiler territory. 

As we explain in our Final Fantasy 7 Rebirth ending explainer, the RPG stays faithful to the source material by seeing Sephiroth skewer Aerith, though here we have an added 'but.' 

Aerith still appears following the event in the boss fight and to Cloud in the following cutscenes. Cloud's ability to see her invites the interpretation that he could be seeing a version of her from a different dimension or is simply refusing to accept reality. What makes it all complicated is that Cloud's party can't see her. They no longer acknowledge her presence and appear deep in mourning. It's been called "confusing as fuck" by many fans who have remained engrossed all the same, me included.

The good news is that Final Fantasy 7 Rebirth's Ultimania book acknowledges the mystery in a section dedicated to the RPG's key points and newly arisen mysteries. The good news just about stops there, though, as the explainer novel seemingly elects to throw up the question: 'Is she dead or alive? Who knows? Not us.' 

While the Ultimania isn't available in English at the time of writing, a fan project dedicated to translating and preserving Final Fantasy 7-related works had done so for parts of the book before taking the work down, though several other reliable fan translators have also summarised what's been said.

Essentially, we have a consensus that Cloud sees something different from what the rest of the party sees. It's depicted through the gameplay as Cloud doesn't start the final boss fight with a full Limit Break gauge, though everyone else does due to how they feel. There's also a nod to the original as the party mourns by where Aerith is buried in the original game,