You can't take away the goalkeeper's movement, because we can control all 10 players on the field, and the only one we don't have complete control over is the goalkeeper, who we can only move sideways, just like you saw in the Championship between Andreas and Phzij. At a high level, this is a skill. If you want to keep Ultimate Team alive, don't remove this, because it will make many stop playing due to the amount of defendable goals they will start conceding.