The Narrative Demands Change
The way that these games have been framed story wise demands a different ending than the original, and the people who think that this game will lead directly back into Advent Children are living in a delusion.
Seems pretty straight forward. (Barret boobs cameo.)
In JP: でもね これからのことは変えられる "But you know what? We can change the future."
Perhaps the most criminal and narratively boring decision in the entirety of the FF7 compilation would be creating this grand, expanded narrative including the meta references to the past titles, only for all of it to be a big red herring or side path to get to the same ending.
The idea that all of these characters are wrong about the future, and everything is one futile struggle toward Advent Children is the complete opposite of what is being shown to us.