Retrilogy is definitively a sequel
The only thing the Retrilogy is a sequel to is Crisis Core and any other assertions require leaps of logic to arrive at that those conclusions. I’m not gonna beat around the bush, I think both the prevailing theories that the trilogy is either a 1:1 remake of OG or a sequel are rather deliberately missing details.
We’ve seen far too much narrative and story change for this to be 1:1. And that’s exactly what the devs set out to do. Honouring the plot of OG while fitting in compilation elements to cleaner weave those elements into the scenario of 7. I don’t think the devs are lying and any theories that require the assumption that they are miss the mark for me, personally. I don’t believe they’d lie about the goals of the project even if I can understand them obfuscating plot details for ongoing releases to maintain interest and mystery. Saying “the devs are liars” in a blanket statement just feels unnecessarily disingenuous.
Things like Cissnei’s story continuing from CC to live in Gongaga protecting Zack’s parents. Introduction of Kyrie and Leslie to setup their stories within The Kids Are Alright. Just a couple examples of how things have changed without deviating from the plot of FF7 that fit compilation content in neatly.
As for sequel theories and changing fate. I’m not gonna act like I know what the devs mean by this. Part 3 drops in a year, we’ll know soon enough. I have my own read on how things seem to be shaping up and I’m open to what’s in store.
What I find curious are the various interpretations of that concept, especially in conjunction with the visions from Chapter 18 of remake. For me, I’ve always tried to ground my thinking around those visions and the conversation of fate with things seen in OG 7. For example, Sephiroth is literally in the lifestream and has been for 5 years by the beginning of OG 7’s scenario. His extra knowledge, given how the lifestream works, can be explained via that mechanism and doesn’t immediately point to Advent Children Sephiroth traveling back in time to change events as many are convinced of.
As for changing fate, I think to the Weapons and how the planet viewed humans as a threat to be extinguished after meteor was summoned. I think changing fate might be more relevant to Aerith activating Holy from within the lifestream to save the planet from the meteor and itself. I don’t think it has anything to do with her living and I expect her happy ending to involve some kind of reunion with Zack knowing they’d have done whatever required from within the lifestream to aid in defeating Sephiroth. The ending of ACC and the most recent novel Dear Destiny both point to that for her.
Finally, on the topic of happy endings, like the devs I’m sure that’s what we all want for the characters. There are already frameworks for how most of the protagonists can have happy endings within the novels. I’m confident some of those will be leveraged to show the characters being happy prior to AC beginning and geostigma spreading. And for the record, the events of AC doesn’t prevent the characters from having a happy ending.