It's doable it's just not logical. You give up a lot of great scoring chances trying for this low percentage move.
The deke itself is easy to do. Understanding you can't do it everywhere takes some basic skill. Doing it 25 times with Sharpshooter players in Competitive modes might as well take 50 games. Very rarely are you in alone on the goalie trying to lure them away from the post for a toe drag shot.
To pull off the shot you need to be on the forehand skating directly at the goalie. Click in on the right stick, pull back, flick up.