Well, never let it be said that I'm not willing to change my mind!
In retrospect I need to get better at telling the difference between "this story lacks a complete argument" and "this story made an argument that I didn't find persuasive." I think my resistance to the movie's ending was that I disagreed with the judgement it reached; i.e. I didn't see what happened between Elio and Oliver as a generally positive thing, although the film clearly implies that we should. To me, the movie would need to allow Elio to confront Oliver about his (to my eye) exploitative and manipulative behavior for me to feel satisfied that the "right" judgement was reached. I ALSO think that the OS is not as developed as it could have been: even including Elio's parents and Marzia, we still don't have enough characters to represent all the 64 character elements we'd expect to find in the OS, meaning that they must have left some out. In fact, the movie definitely leaves out at least one: Vimini, who I suspect served an important function of rounding out the OS argument in the book.
I really like that in the storyform I identified above, Progress is the benchmark for Elio's throughline, which is what you initially identified as the OS goal. I think your intuition that Progress plays an important role in the storyform was correct. But here, it's more the way we measure Elio's progress towards his goal, rather than the goal itself.
I think the book might have the same storyform, actually, but that the final section acts as an extended author's proof that Elio's resolve never changes. He stays loyal to the idea/memory of his love with Oliver, and never again finds a partner who affects him in the same way. In other words, he never truly lets go of Oliver, so the story consequences of Obtaining stay in place. This proves that he remains steadfast. This is another thing that the storyform I identified makes clear: Oliver is definitely the change character. The movie leaves the nature of his change a bit vague, which to me is a weakness, although others are welcome to disagree.