Whether or not Uther is a good teacher is a tricky question, and the basic point is that people (characters and players) have different expectations of Uther.
If by teacher standards, Uther is a qualified teacher. He educated Arthas with all his life's knowledge and skills, and at the first level of the Terran campaign, Arthas expressed the hope that King Uther's patience would affect him. Uther's teachings were a bit rigid and inflexible, but they were not a big deal for an old paladin who had reached retirement age (Uther was over sixty by the time Arthas came of age), and Uther was heading towards the grave and could not be expected to keep up with the changing times and deal with the treacherous court.
If you follow the standard of the teacher, Uther is still qualified. Arthas's joining the Knights of the Hands of the Best, receiving training and blessing to become a paladin was the guarantee and personal efforts of Uther, who withstood the pressure and doubts within the Knights, and trained Arthas by himself. The Lightbringer risked pointing fingers and even ruining his reputation to pave the way for Arthas himself, and it is not an exaggeration to say that he was a mentor, especially when the Light blessed Arthas at the paladin ceremony held in Stormwind, which was noticed by some of the invitees. If anything goes wrong with Arthas, the first thing to do is Uther's need to take the blame.
If by Sir Lothar's standards, Uther really can't, and the disposition in Stratholm is completely unqualified. But the problem is that Sir Lothar is a nobleman of the Stormwind Kingdom, the Supreme Commander of the Stormwind Kingdom, and the regent of the Stormwind Kingdom, and after King Ryan's assassination, Sir Lothar was the veritable ruler of the Stormwind Kingdom. In contrast, Uther is the commander of the Knights of the Silver Hand, not a nobleman of Lordaeron, unable to command Lordaeron's army, unable to announce the takeover of the army by the head of Arthas, and is not treated at all as well as Sir Lothar.
He taught Alsace to believe in the Light, which in itself was not wrong. The Holy Light Sect was originally the faith of the Human Alliance, and the Paladin became an important force in the Alliance after the Orc invasion, what did he believe if he didn't believe in the Holy Light? He trained Arthas as the next commander of the Knights of the Hands of the **, which in itself was not a problem. He taught Arthas not to be blinded by hatred, which was also correct and valuable, and also laid the groundwork for the blackening of Arthas.
As for the Stratholme incident, this is not a question of "Teacher Uther", but of "Uther, the head of the Knights of the Hand". As a teacher, all he can do is advise. He persuaded him, but Alsace, a stunned young man, was already on his head, and if he didn't listen, he couldn't help it. But as the head of the Knights of the Hands of the **, he has to solve problems for the country. Now Stratholme is caught in the problem of zombification of all employees at any time, and the crown prince wants to stay to deal with this matter, he, as an important minister of the country, actually has a temper with a stunned young man, and leaves with the backbone of the country, putting the crown prince in danger. This TM is blatant dereliction of duty. Therefore, Uther has no problem as a teacher, but he has a big problem as a royal court minister in an important position.
First of all, the Hand was created by Archbishop Fao and his followers to protect humanity and its allies from the orc threat. At the beginning of the reign of chaos, it was clearly stated that the orc movement was instigated by the demon (Burning Legion), and that the threat of the cursed sect, Uther himself, had been directly taught in Anhador, and encountered such a problem as Stratholme.
No matter what the prince intends to do, the Knights of Yugong should prioritize the protection of civilians and the fight against demons, rather than abandon their allies and leave, and Dare 2234 is not a member of your Knights? Abandoning his fellow allies, the people, even an impostor like Dasohan could not be clearly understood, and Uther did it in front of the whole army. Come to think of it, if the Templars had turned around and slipped away while Bao Si was charging the Saracens, would they still have the life to return to Jerusalem?