- Saving Madara isn't Hashirama's job, Madara is his own person and will do what he wants so that's not a mistake on Hashirama part. Madara is the cause of his own problems and what force would he even need? He was working on trying to get all of the clans to move pass their clans and see the village as a whole as their family. His mistake was trying to make Madara Hokage without asking the council members or villagers what they want but Tobirama set him straight on that.
How was moving the Uchiha's out a mistake when most of them were running wild with a hatred more stronger than the love they had for someone or something they lost? So it's a mistake trying to protect the other clans from this behavior? No one had fear of the Uchihas for the Police force, they were just disliked by those they arrested or dealt with as many people irl seem to have with real cops. This would have happened with others acting as the Police force, Tobirama only gave the Uchihas this role since it's something they would be good at. The fear and distrust really came when Danzo made the Uchihas not help when Kurama was attacking the village because the villagers didn't know why the Uchihas wouldn't have which caused many people to die and they started to think the Uchihas were behind it. Here's Tobirama talking about Hashirama and his role
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and
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.Hiruzen did mess up in letting Danzo handle the deeds in the shadow because he was to kind of a person to do them or to try and handle the issue. He also did say he failed to continue Tobirama's work
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.Minato wasn't the team leader of Kakashi, Obito, and Rin anymore since they were Chunins and Jounin in Kakashi Gaiden and he was only really their leader when they were Genins. They are grouped together because they grew as a team but at Chunin level they are usually placed in different teams that the Hokage would make for different missions. Jounins can go on missions themselves or lead other teams. Kakashi was the official leader of Obito and Rin so Obito's supposedly death was on Kakashi more, same with Rin's death. Minato actually did stop the attack, he beat Obito then went after Kurama. Kushina would have lived if Minato let her seal Kurama back into herself to die with her since we know she would have in fact lived like Naruto did but they didn't have that info and Minato didn't want Kurama to revive later on hostless because it would be dangerous for others as well as mess up the balance of power amongst the villages.
Tsunade wasn't even in the Village when Oro attacked, she left Konoha long before the Naruto series time line started so how is that her mistake? How is failing to protect the village a mistake? She was simply not strong enough but tried her best to protect the villagers. Being weaker than the enemy isn't a mistake since they can't do something correct there; they are as strong as they are. Being weaker than Madara who grew in a time of constant war is not a mistake, that means you want the Kages to all live in a time of constant war so they would be more skilled than they are from their peaceful time and at least 1 war that happened, ended, then a long time of peace before another war.
Hiruzen made the real mistakes as he said but he was still a great Hokage as well.