Pokémon Go, while perhaps not the best use of anyone's time (including Muslims), is a game. It does not promote violence, does not promote sexuality, and does not promote godlessness. Any religion, including Islam, that attempts to say that a game cannot be played by members of that faith group is absurd and cult-like.
The virtual reality game Pokemon Go has enjoyed an incredible amount of success. The rules of Islam do not apply to videogame activity so they should not and, indeed, cannot prohibit the activities created by this popular game. No religion has the right to limit what people choose to do in their free time.
I believe Islam should prohibit this game. Islam believes there is one true God and every human was created to obey and serve God. My view is the game is not wrong. However, it does not fit within the Islam Religion. The game does not in any way serve God or others in any way.
Pokemon Go is merely a fun game that gets people out of their homes and into the real world. It does not violate the tenants of Islam in any way. The only problem is if a person spends so much time playing Pokemon Go that they neglect their other duties.