I'm not a coach either, but that's part of the point: most of this stuff isn't rocket science. I don't see the point of "saving" strategies for the playoffs (Denver certainly didn't against the C's). Most of the playoffs are reactive: one team tries something, the other team counters. My point is that Joe has traditionally been slow to react. There's reason for that based on the success of the team's offense (they haven't needed to) but he's going to need to do it in the playoffs against a team like Denver that doesn't get easily beat off the dribble.
We also saw Joe's limitations at the end of the Cavs game. Again, he relied on Tatum to initiate the offense and Tatum was going too slow. Instead of giving Tatum a sign to hurry things up (or God forbid run a play), he stood there and watched his best player order a clear out that went nowhere. When Joe finally realized things weren't going well it was too late. He apparently tried calling timeout with 4 seconds left (which, to my knowledge, nobody saw), but by then he had already waited too long.
A lot of people blame Tatum for his poor play against Denver and for his poor execution at the end of the Cavs game, but I think the blame goes to Joe in both cases. If things are going south you can't just wait and wait and hope your players figure things out. You have to employ strategies that counter what the other team is doing.
Now I like Joe and think he's a good coach but he has limitations and those limitations can be exploited by very good teams and very good coaches (Mark Daigneault, for example, is someone I think could give Joe problems in a series).