But for anyone in management, it's part of their job to get the most out of their employees. If they can't then I'd say they are not performing their duties. As for your teacher reference, I'd say that if those students with poor educational backgrounds didn't show some signs of growth during their time with you, then yes that would reflect on you.
And it's not just a hockey thing, it's a sports thing. Professional sports is a results driven buisness. If you don't get results, you get replaced.
I feel like I have semi-relevant 'history' here since I just finished up a management course at university.
When motivating and getting the most out of employees, there are a set of processes you undertake and stand by as an organization, that should help in aligning the work done by employees to the organizational goals. One of the bigger ideas in this is the control process, where you establish standards for performance, measure performance, compare the two, and then 'correct deviations'. Conventionaly you look at Sigalet, and say you expect an NHL level goaltender, he didn't do it, you need to correct the deviations there. But part of correcting deviations is taking a look the cause of the split between expectations and reality, and adjusing the expectations based upon that.
So if we look at what Sigalet has done, he failed to meet the initial expectations of reforming Hiller and all them, but it was based on the assumption that we are giving him a complete product to work with. So when we see a split of Sigalet getting them to work for a short period of time with no sustained success, we also need to look at the supply of those goaltenders which is what Fig is doing. So for the stretch following Kippursoff the NHL-ready goaltenders brought in have already been discussed, and Gillies and Parsons were hit by injuries (Gillies especially with hip surgery early on in his career iirc) so we can't consider those complete products under his care, and MacDonald was just a yikes pick from the get-go. So the criteria where we expect Sigalet to turn these players into future starters is unreasonable, and it's unfair to judge him off of his ability to work with NHL level goaltenders based upon that. Then we look to more recent history where he has had Talbot, Smith, and Rittich. All NHL-calibre goaltenders. Smith was successful and almost drove us to the playoffs before getting injured and even when he wasn't successful the fact that he bounced back could in part be due to coaching help, Talbot credits Sigalet with rejuvenating his career, Rittich has shown flashes of being a starter but keeps getting injured. By the criteria of helping NHL-level talent it is hard to argue Sigalet hasn't been successful.
Giving a baseline criteria for Sigalet to fill in for every single goalie we get into the organization is a flawed idea, in management you need to set goals with nuance built in, instead of making the assumption that the product he gets is perfect. I think we should judge his contributions with some goalies under the frame that he is extending their career to give the Flames some form of net-presence between prospects hitting the scene (Hiller, Ortio, Ramo), while when getting NHL-calibre talent that is healthy he should be judged for their performance the way we try to do for the guys who left the league shortly after being in the system. Getting results is always valued above all else but there is nuance to what reasonable results and expectations are.