There are a lot of things that factor into your shooting including, the most obvious, the player's shooting stats. What most people don't realize is that the player's body angle to the goal and most importantly, pressure from the defenders affects your shots A LOT.
You'll notice you're on target more so when there's little or no pressure on your player and you don't have him trying to shoot from crazy angles. Unless the player is extremely good (high stats) your shots are going to be going up in the air!