“Just on a basic level though, why does Kylo’s redemption have to be a part of Rey’s story?”
I don’t know how else to answer this for you! LOL. By the point his redemption becomes legitimately viable, it’s firmly her story and he’s HER villain. He’s not a supporting or secondary protagonist. I don’t understand how you possibly make his redemption NOT in service to her story under those circumstances, and those ARE the circumstances by the time his redemption is seriously on the table. It’s not a what-if or a hypothetical at that point. It’s 2 1/2 movies into a 3 movie cycle that is absolutely her story, and his place IN that story is just as firm and absolute. He’s the villain of her story. His redemption needs to be in service to that to be successful.
Well, that’s brings us to a different line of discussion. If he’s redeemed, who is she up against? That was the central question that forced JJ to bring back Palpatine, so I guess I’m starting to see your train of thought as to why this was sort of the incept point for things going wrong with TROS.
But there’s a few things to consider. First of all, the Palpatine aspect of TROS was pretty bad, but it wasn’t inherently bad - there are ways it could have been done better. Second, there were other villains who could have stepped in - you have the whole First Order, Hux, and the unused potential of the Knights of Ren to consider. Finally, Rey’s main conflict this trilogy has never been her vs. Kylo Ren. It’s always been her vs. herself and her perception of who she is and who she can be. One of the few right ideas (executed poorly) that they had for TROS was that the main threat for Rey was herself, and her own potential for the dark side. When she fights Kylo, she beats him, but it’s a failure because she’s acted out in anger. That’s smart, regardless of execution. I think there are many ways they could have followed down this path of Rey, rather than Kylo, being the villain of her own story. In my mind that’s the proper continuation of what’s been set up. To me, super powered good Rey facing off against super powered evil Kylo as the climax of the film/trilogy/saga is boring. That’s why the DOTF confrontation is so lame. These characters should be more complicated than that.
That’s why, in my mind, Kylo shouldn’t Rey’s final antagonist in IX. In TLJ for most of the film her antagonist is actually Luke, then Snoke, and only becomes Kylo again at the end. Yet, despite this, they have a now have a much more complex relationship than the typical good guy/bad guy. DOTF abandons this complexity for the worse. TROS at least attempts to continue with it, even if it’s not handled so elegantly.