Agreed Scheer was a lousy speaker unlike Miliken.  The only thing he has in his favour was his young age as most in their 30s don't tend to have the same level of life experience as those in their 50s and 60s.  If you look at Trudeau's cabinet, it is the younger ones like Monsef who have messed up most not the older more experienced ones like Goodale.  As for whether he gets another chance or not, if the party performs around the same or worse, no he is gone as leader, but if they improve in both seats and popular vote but still come up short he will get another shot.  But that would likely mean a minority government so 2021, not 2023 would be the test and if Trudeau wins then he is gone, so I think if he cannot be PM by 2021 he is gone.