Halo 5 is sure controversial, the games has positive pr and a positive praise from a mainstream media but at the same time has a negative review from blogger and small site, and also negative news from sales data, so Positive + negative equal = Zero. SO the logic is Halo 5 is a decent games ( not fail, but also not a success games ).
But It failed on helping Xbox one sales closing the gap. And also it's a fatal mistake, because it need to have at least minimum 95 review score, because it's the only reason "most "of Xbox fans buy Xbox one.