When Leafs fans talk about Keefe's resistance to make changes, they're not talking about the regular season. Keefe had a 69 goal scorer/100+ point player and 2 more 98+ point forwards - he's going to win regular season games regardless of whether or not he made adjustments. The Leafs never won their division though - aside from the Covid North division so there's definitely room for improvement there also.
Slow to make changes is in reference to when things aren't working, he refuses to change things and thinks if he keeps repeating the same thing the results will come. It happened this playoffs with Samsonov. He didn't switch to Woll until the Leafs faced elimination leaving the Leafs 0 margin for error despite Samsonov playing horrible 2/4 games he played prior. When the Leafs scored a goal to take the lead or tie a game, Keefe always went to the third/4th line to go get some hits and it resulted in a bunch of goals against the Leafs - including in this year's playoffs.
Keefe has basically been a coach with a game plan that will not adjust his gameplan if the results don't occur. He believes in the plan he puts in place and will ride it out with his belief of that plan. Since the Leafs haven't had success with his plan, the fanbase blames him for his lack of adjustments. Ryan O'Rielly said after the playoffs last season that the Leafs 'could have made some changes but didn't' and that pissed the fanbase off and they took it as Keefe's stubbornness to listen with rumors RoR suggested changing something and Keefe refusing. He was a very live by the sword, die by the sword coach. He believes in his process and won't usually make adjustments.
That said, I think New Jersey got a good coach. I thought Keefe this year was the best he's ever been as the Leafs coach. This year he got extremely unlucky with injuries in the playoffs with Matthews, Nylander and Woll all missing games. This year he basically paid for his failures in previous seasons when he should have won but didn't. He was a lot more calm and composed this year and seemed a lot less hyper on the bench. The officials don't seem to be a fan of him complaining after every call and he did a lot less of that this year, especially in the playoffs. It does seem he is growing and learning from his mistakes. More importantly, he seems to be a quality person that people like - which was the opposite of the Leafs previous coach. I wish him and NJ the best (except when they play the Leafs). He's a very structured and details oriented coach. He seems very analytics minded and that's why Dubas took him everywhere he went. He'll make a plan prior to the game and stick with it through and through. He believes in himself and his gameplan and that of itself I think is important. However, when it doesn't work he gets blamed for 'lack of adjustments' which is what the Leafs fanbase is on him about.
