This film plays a lot with the advantage of not being a canon with the One Piece manga, so it brings characters from all sides and creates situations that in the official manga canon could not be possible, such as Bonnie and Sabo being together in the Reverie, for the fans of the series or the manga this movie is to be able to see interactions between characters that in the manga would never see interact, of course, the movie takes too much of the fan service, although it is not at Marineford level the number of characters faced. That can compete with many official arches.
One of the problems that were expected of the film is that having so many characters together would not be able to develop each one well, however, he surprised in this aspect by not failing, by handling his great cast very well. In the movie there are 3 groups of characters, the Straw Hat, the supernova and the 7 fighters that were promoted in the promotional material, all receive a great development in history and fights develop to see the potential of each character, then there is a lot of secondary characters but equally more than one has a scene in which they shine.
One thing that One Piece does very well on the big screen is that it gives anime and manga fans things to enjoy, lots of cameos and Easter eggs, sometimes too difficult to capture, like the Arabasta seller, but It's something made for true fans of the series or manga.
The antagonist is a really strong character, only behind the Yonkos and certain characters, and finally a One Piece movie where the antagonist is not someone like Treasure, Shiki or Z, but still with a huge force that sows fear of defeating too much a lot of strong characters of the canon, however in terms of plot is not a character as deep as Z or Shiki, which takes away the character's quality.
What can be said is that the film develops more fights and conflicts between characters than the plot as such, and in the breaths it has is the moment in which they develop the character of Bullet, but also 60-70% of the movie is based on trying to defeat Bullet, again and again, joining forces several characters.
A problem that does not handle quite well is that as there are so many characters and only 1 antagonist, the not-so-main characters really are there to be, because they do not contribute anything to the fight against the final villain, it is not a pity but to include more others characters would make the movie a lot better
The film stands out at the time of the choreography of the characters fighting, it is incredible how well designed the fight scenes are, how the camera moves and how to destroy the battle environment, there is a great 3D animation and CGI behind of this film what makes it incredibly good to see
The soundtrack does not stand out but does what is necessary, sets the battles and the moments of calm very well, which in the end is what matters of a good soundtrack, and in short One Piece Stampede is a movie for fans, which always wanted to see impossible situations and fights.