Coaching is like scouting, you're dealing with complex evaluations, many of which will inevitably be wrong ex-post.
The first step in evaluation is the team situation, in a rebuild player development is the primary goal, winning games has value to the extent it helps player development. So benching young players to get a message across, sheltering young players, etc. is part of that process. Look around the league at top young players whose development was throttled by a HC putting them in over their head, in a bad situation, etc.
Once a team is competitive, the HC is coaching for a 100 game season, keeping veterans fresh, etc.
TC and the first month or two are different animals than the spring, each year a HC has to experiment and find out how new players fit the team and his schemes. Anyone who actually watches games knows that fit and chemistry is important, this isn't EA sports where you put together the guys with the highest ratings and play them as many minutes as possible. It's more like a jigsaw puzzle, not overworking your stars (so they have fresh legs in April), sheltering limited or inexperienced players. Finding the right combos for lines and defensive pairs and special team units. And you have to play different groups, both b/c the flow of the game requires it (penalties, dings, a star playing too many minutes) and because injuries are inevitable so you need to be prepared.
Judging a HC's decision out of this context simply exposes a lack of knowledge.
And each season is a separate story, a HC can do a great job and be deep sixed by a goalie, or conversely, a mediocre team can go on a run behind a hot goalie.
