I would say all stories (or almost all stories) have recurring elements or archetypes, however I wouldn't say all of them are derivative. Many of the greatest stories written have an amalgamation of more than one such archetype or said element is shown from different angle.

I can see AI helping writers with stuff like dialogue or being more eloquent, maybe imitating a specific style. However the issue is that AI doesn't understand what is being written. It is likely that it would write nonsensical sentences.

If AI can reach the level of general intelligence, so it understands context, than it can possibly "write" somekind of story - likely still very derivative, but coherent. The issue is it's still very far away, if it's possible at all.

AI can be trained on a huge number of art and can simulate the style of an author/poet. However AI can't create their own art, they can only create derivative art. Even than as the AI doesn't understand what's it's doing it'll likely have nonsensical parts, especially if it's a longer work. So it's basically creates glorified fanart.

If AI can reach general intelligence, so it actually understands what it's doing, then it can create new art. That said it's questionable if AI can reach general intelligence (it is possible, but not 100% sure) and if it reaches it, than when will it be.

I cen see your point and maybe it's my worldview that resonates more with Dostoevsky's, but to me the epilogue was a very nice "send off" for Raskolnikov. But as I said, I can see why it's not for everyone.

I think it very much depends on the story. Crime and Punishment by Fyodor Dostoevsky, had a relatively short epilogue (if my memory serves me right), but it was crucial for the story.