"Metacritic scores don't really matter to me as I remember Game Informer"
That's kind of the point of Metacritic. It makes it so a single stupid review doesn't destroy the general consensus.
Also, if your "co-op grrr!" theory held any water, then it would also hold true for Dead Space 2's throw-away competitive multiplayer. It didn't though. No, DS3 is simply a lower quality product than the previous two titles. If you like it? Hey, great! More power to you. The general feeling though is that it has skewed heavily away from it's horror roots and more toward the COD set pieces that we all became bored with two years ago. It's a game without direction, without soul, and infected with F2P mechanics. It's the Forza Horizon of third person shooters.