In the personnel management inside the Great Wall, he only paid attention to stability, ignoring various contradictions, including coach Alisha Thorne's insults and insults to recruits, which led to the hostility between Jon and Alisha. Ignoring the night watchman's dissatisfaction with Castel fortress, the contradiction intensified, which caused some night watchman's resistance and directly led to his own death. Faced with internal problems, he obviously doesn't want to make changes. He always hoped that the contradiction would subside and did not take concrete measures to change the status quo. Finally, the conflict broke out and he was legally controlled. He is too radical to treat aliens and barbarians outside the Great Wall.
He ordered the bodies of two rangers to be brought back to castle black for research. As a result, the body became a ghost, killing many night watchmans. If Jon and the ghost hadn't been rescued, he might have died. Facing a series of unknown events outside the Great Wall, he led 300 elite night watchman expeditions radically, which led to most of the night watchman expeditions being strangled by strange ghosts at the fist peak of their ancestors, while the rest were wiped out at castel Castle (including traitors) and returned to the Great Wall. On the whole, Commander Mormont was too steady at home and too radical at abroad, which led to the heavy losses of the already weak Night's Watch Corps during his term of office and left a mess for his successor Jon after his death.
Although this is inseparable from external uncontrollable factors (such as the appearance of alien ghosts and the gathering of savages), as commander-in-chief, he is hard to blame.
The most correct thing he did as commander-in-chief was to choose Jon as his successor and visit the Great Wall. Jon is the only one who can save the night watchman!