Why it failed: Bad actors
This movie could have been more well regarded instead of forgotten otherwise. It had an interesting concept of a futuristic advanced capitalist dystopia. But the problem is the two main actors were awful. As well as those in supporting roles.
Justin Timberlake was a R&B/Pop singer cast in this relatively serious role and couldn't deliver. He was also a bit too old for the character. He could not act in the film or deliver the emotion needed. Amanda Seyfried was also not leading lady material. Not really a great actress and not beautiful or sexy enough for a role like this. Not too mention boy, was that a silly looking wig she wore in the film.
Just my thoughts. Better actors would have made this film memorable.