I don't have the experience playing as a goaltender, but they are too much at the mercy of X-Factors, screening is too wide (and they don't look around them properly), the covering animations are horrendous (and poorly timed), the poke checks (computer goaltender) are predictable and can be taken advantage of, they give up terrible rebounds too often (professional goaltenders at least attempt to deflect pucks to the corner), scrambles are too frequent and the goaltender tires too easily, own goals or the goaltender knocking the puck into his own net are way too frequent as well.
That's one big messy paragraph of some of the things that need to be looked at off the top of my head.