That was a freaking delight!
Since DX was pure fan-service and after the mild disappointment of DX2 being as safe as it possibly could, I didn't want to keep my hopes high for the rest of the crossover movies being more than extra icing on top of their season's cake. It's a good thing that DX3 not only blew my expectations out of the water with its solid writing and genuine character moments, but it also dared tell a bolder story and fake us out with a bittersweet ending up until the post credits scene!
None of the scenes felt like padding, each one having a clear purpose in the story; the character moments felt more genuine, and most importantly, the new Cures had their moment to shine! DX did the Fresh trio dirty by wasting too much time on references and callbacks, and DX2 was too unfocused to do anything effective with the Heartcatch duo. Conversely, DX3 had the new girls meet and learn from their seniors, take those lessons to heart and then use them in act 3 for the climactic final battle. That's good writing, baby!
Of course, nothing is perfect. The start of the movie, in the choice to get right into it, felt way too rushed; yes, we know those characters already, and I get why you'd just cut to the chase, but it's the fact that I know these characters that makes me want to spend more time with them, you know? It was one of the things DX2 got right -- spend 10 minutes just hanging out with the Cures. It's part of the 3 act structure: set-up, confrontation, resolution. If you put the inciting incident right at the 2-minute mark, it makes it harder for the audience to immerse itself in the story.
All that being said, though, I enjoyed this movie way more than the previous two. As always the animation is impeccable, the action is spectacular, the music is-- well, the same as always, and I almost didn't want to kill Coco this time! That's progress.
9/10 - if you're going to watch any of the crossover movies, watch this one.