Even if he had held the catch, doubt it would have made much of a difference in the end result. 12-13 runs an over in last 4-5 overs are normal occurrence in this day and age.
Next man in, Pat Cummins is a lusty six hitter as well, even starch can hit it a long way. Stoinis set man was already there. Specially In day and night matches in UAE batting second is much easier due to dew, only way to win matches is to have opposition minimum 6-7 down by the end of 15th over, with them needing more than 10 an over. 5 wickets or more in hand in last 5 overs, teams can chase down 65-70. Happened in NZ v ENG game. NZ needed 57 in 4 overs, they chased it down with an over to spare, as they had 5 wickets in hand. Aus needed 50 in last 4 and chased it with an over to spare. So for team fielding second every opportunity has to be taken, Australia presented a few but Pakistan couldn't take advantage of it. Run out miss of wade when Aus was 103/5 and run out miss of stoinis at 110/5 was the turning point of the match.
Hassan Ali was out of sort throughout the tournament yet he was persisted with, it was more of team management fault that they didn't look out for alternative option in matches against Scotland and Namibia. Sure, he was trying his best but lacked form and confidence and had a tournament he'd like to forget.
Overall the team fought till the end and deserves appreciation for performance on and off the field.