Don't forget Hiruzen with Orochimaru. Definitely don't forget that.
But I agree, they were all extremely biased, making them partially bad at their jobs as teachers. Let's be real here, some teachers were just bad and unlike Kakashi, didn't have screentime to make up for that mistake. Let's see...Minato left his team basically dysfunctional and relying on an arrogant and cold Kakashi, while Obito and Rin were worth fuck all in a fight against adult ninjas, getting Obito to being Madara's pawn and Rin killed. All of that because of the war and Minato not having the time to babysit three kids with unresolved problems and doing cool shit to protect his village. As great as Minato was, he clearly made a massive mistake.
Look, I love Minato, but this is just my reading into the situation. Shallow and oversimplified, I know, but that's just my way of reading things.