The earlier Spider-Man movies did well, but Spider-Man 3 shows Sam Raimi struggling with a common problem of sequels—outside pressures getting in the way, like what happened with Alien 3, The Godfather Part 3, RoboCop 3, and many others. I had hoped that was the sole issue affecting this film. However, nearly every choice made in terms of the story—introducing Sandman, Peter’s sudden affection for his new suit, and whatever that black goo character was supposed to be—feels misguided. From the start, it's hard to like Peter Parker. It wasn’t a studio mandate that led to the jazz bar dance sequence or the confusing Green Goblin subplot. The love triangle involving Gwen and Mary Jane also felt wrongheaded, contradicting what Peter Parker is meant to represent. These were serious problems with the writing and how the film was directed; they essentially sealed its fate. That’s why this movie is disappointing, not just because of how poorly Venom was handled.

Source on TMDB