This movie is a big miss.
1. Soundtrack in Guardians 1 was important for explaining Peter's history and made the movie relatable for the audience. In Guardians 3 the soundtrack does not have the same resonance, and in fact they throw in a few too many songs to keep the pace going. Peter going back to save his I-pod in this movie was just an unimaginative repetition of what he did in Guardians 1.
2. The villain of this movie seems incredibly lame after Thanos, who was powerful enough to alter the universe. This guy just seemed pathetic, made worse by the stupid costume.
3. I felt really let down when the kids in the cages appeared toward the end. This just seemed like insurance that writer/director Gunn threw in to make the villain seem worse, in case the audience wasn't already upset by the mistreatment of animals and the destruction of a planet. An underconfident move by Gunn in a script he may have sensed wasn't up to snuff.
4. Along with the previous point, Gunn throws too many plot points into the grab bag of this movie to try to make it interesting, an attempt that has the opposite effect. For example, what happens to Peter's alcoholism? After he passes out at the beginning, that thread is never carried through.
5. This movie has absolutely none of the spontaneity, sympathetic characterization and sense of fun of the first movie. I don't care what happens to any of them in future Marvel movies. Wish I had stopped watching after Guardians 1.