Sounds like the opponent's defenders are in the right positions to block your shots. Try placing your attacking players in positions where they will not be blocked by an enemy defender, or if that's not possible, focus on where his defenders are the weakest.

You can also try to focus on Shooting and Finishing attributes in your training sessions. It will improve your player's ability to shoot accurately and score.

On average my shot accuracy is anywhere between 30% and 50%.