That's not his fault per se, it is just our (one & only?) corner routine is that the ball has to be placed into a very small window of 'just' over the near post defender but not too high over them, as then the keeper will catch it, along the edge of the 6 yard box for the runners to attack.
I'm sure the stats will show that when a corner goes into that small window there is higher chance of a goal, it is just we are unable to deliver the ball into it regularly enough to make it a dangerous weapon for us.
If we want to persist with it, one person has to run in to the front post & if it doesn't look like its high enough to beat their man at the near post try & get a flick on or disrupte the clearance.