He has no presence at the crease and cannot impose himself on the opposition. He is our so-called senior batsman, but opposition bowlers don’t view him as a threat.
Even if he bats for two days, he will not put Pakistan in a commanding position.
Shafiq has a lower average than Azhar but he's played many innings in the past which changed the course of the game.
Imam, Azhar, (potentially the batsman Sarfraz) are all in the same category. We may draw/win this series with them in, but for consistency they need to be dropped.