I thought the Finn/Rose/DJ plot arc was one of the better part of the film. Was it squeezed into the film that was already trying too much? Sure, but that's a greater fault of the overall directing and writing to put so much in so little time. Personally, I would have been OK with that whole plot being made into its own film like Rogue One.
It was definitely contrived but not anymore than the rest of the film. In terms of characters, Finn sees a lot of character development over that arc. Rose is a bit more flat, but she's the foil to Finn, serving to give him a reason to fight. Then toss in DJ whose loose allegiance adds a much needed shade of gray into the universe. Are we suppose to believe that every rogue has a heart of gold and will fight for the Resistance/Rebellion/Republic?
I was half expecting the First Order to execute DJ but was very glad they didn't. The Empire and First Order aren't supposed to be evil for the sake of being evil. I thought it was a very poor portrayal in some of the earlier films where the Empire kills the Trade Federation leaders for seemingly no real purpose other than to show how evil they were. The whole arc demonstrates the resourcefulness and fairness of the First Order as a regime and why people in the Universe would actually agree to having them around. It demonstrates the prudence of DJ, who while empathetic to Rose and Finn (going so far as to giving back Rose her necklace), is ultimately a pragmatic individual. It demonstrates that placing your trust in strangers, a reoccurring theme in the films, is a dangerous decision, something that's never really shown in the films. I hope this is the last we see of DJ because I don't want them to turn him into yet another rogue with a heart of gold (i.e. Solo, Lando) or to make him into somekind of villain, which is not the purpose of his character.
If it had been its own film, I would put it alongside Rogue One, forming a sort of anthology series that explores what kind of people inhabit the universe.
