This is just where we disagree, the thing is they didn't end up in different places. Kylo is still first order and the resistance (with rey poe finn) is still the resistance at the end. There's no progression of story, just a re-telling of the same characters arc(s). There's very little actual advancement because the characters weren't properly developed in the first place. There's no reaction or consequence to their choices by the end. That's why I keep reiterating that was just subversion on RJ part, there was very little "new" in terms of advancement of story and character overall (aside from Luke).
That's the thing though. Him being in the first order isn't a sign of him not changing. His viewpoint from movie one to the end of movie two has changed. His status has changed within the first order. That's progression. Rey is in a different place at the end of last Jedi than she is at the end of force awakens, as she should be. As is Poe. Even Finn, if you squint lol, is in a different place where he goes from wanting to fight purely for one person (Rey) to fighting for a group and realizing the totality is greater than the one. Or as Spock would say, the needs of the many outweigh the needs of the few. If you want to argue execution of said arcs, that's fine, but all these characters are in different places by the time the credits roll, even if they have the flimsiest of starting points