Oh yeah, the premise of Advent Children isn’t inherently bad, but you can definitely feel that it started as something else.As far as AC is concerned, it's hard to get to the bottom of the story, because they'll never say explicitly that it's just an order to make easy money on FF7. Which, let's face it, is what the Compilation project is all about.
All we know from the itw with Nojima is that in his mind, post-FF7 was an everyday story about the couple Tifa and Cloud, but that Nomura came to him wanting a high-stakes action movie with an emo Cloud “because that's how people remember him”, so he had to adapt and come up with something that made sense.
When you look at it as a whole, it does. The state of the world with a destroyed Shinra, Sephiroth resisting and not dissolving into the LS and his attempt to corrupt the planet right to its core. It all makes sense. It's the execution that's not so great.
Honestly, if they end part 3 with the original concept that Nojima wanted, a happy day with Cloud, Tifa, and the kids, then I’d consider it a closed book imo. ACC was the low of their relationship, leave me on a high note and leave me with the closure that they end up happy.