I mean, it won't stop teens and pre-teens from playing. I was under 18 when Halo CE came out, and my parents were pretty strict about violent games, but I still managed to play it. The only real difference an M rating would make is that they'd be allowed to show actual animated blood when we kill enemies, and there could be swearing in the dialogue. That's not going to fix the story. Hopefully they'll learn from the criticism of the Grimoire card system and deliver more of the story through in-game dialogue in 2 though.