That's what is wrong with many games this day and age. Everything has to do with the multiplayer. Whatever happened to just creative writing, and interesting characters. Even Halo has fallen victim to this, I personally think Halo 3's campaign was pretty sloppy. And Reach's wasn't very extraordinary either.
If it were up to me I would take matchmaking our of Halo and leave it so that it is just a strong story based game. Spartan Ops would stay as it seems to be story driven too.
But it does seem that 343 is trying to change the past few years of Halo story telling via video games which I think is good. Make a solid story, make Master Chief actually interesting, etc.