The thing is, you can still make a darker more action packed movie and still make it feel like Star Trek. Just look at First Contact, some of the more intense episodes of DS9 or even the upcoming fan film Axanar.
True. First Contact is the best Star Trek movie of all time, in my opinion. Yes, it has action, but it still keeps to the diversity, space exploration, and search for knowledge themes. But this movie seems like the producers realized that Trekkie fandom isn't what it used to be, especially with new Star Wars movies in the works and other space movies like Gravity, Interstellar, and The Martian. Then they watched "Guardians of the Galaxy" and said "That was brilliant, we need to rip it off!"