Do you mean the stubbornness where his team out shot Columbus 33 to 21 in game 5, but a .905 SV% performance by his goalie cost them the series, or do you mean his stubbornness where his team out shot, and out chanced the Habs this year in games 5, 6, and 7, but a .892 SV% performance cost them this one.
A goalie is part of the team, and its the coach's job to get the best out of his team. If your arguing Campbell cost us the series with poor play in game 5-7 (ignoring all the bad plays made by the players, including Sandin's 2 giveaway goals, Dermott and galchenyuk's, Marner's giveaway/penalties etc) then I'd say go watch the games again.
We out chanced the habs in-game 5/6 and didn't win. Keefe decided to run back MM+AM duo along with a struggling Hyman, giving them 24 and 25 minutes for the night, with neither being able to convert anything
In 2020, he brought back AJ into the lineup while after months into an elimination game. He decided to go with a super line and had Nylander playing center for one of the few times in the year.
In 2021, he broke up the strong producing 2nd line taking out Galch off the line for Foligno, he brought Sandin in who cost us game 5 for Dermott who we won in game 4.
He was never able to get the PP units working and let the PP coach continue operating the same units with same plays that weren't working. Joe Thornton for some inexplicable reason continued to get PP time despite being very slow and unworthy of the role.
Keefe has been given as good at least as good a defensive core as the contending leafs of the early 2000s were. He has higher high-end talent than any recent previous leaf team, and while the offensive depth has dwindled the team is still built to at least be capable of winning 1 round.
He has played some of the worst playoff teams possible, getting an 18th seeded Montreal, along with a fringe team like the Jackets. He's lost series to offensively inept teams, with the leafs not likely to ever get as easy matchups as they did the past two years which were blown by Keefe and the team