Brad Stevens is not a championship level coach IMO. I think the players we have are soft, but i think the biggest problem is coaching. His rotations are terrible and always have been. He never plays anyone big minutes no matter how the game is going or if the game dictates playing guys big minutes. He is a really nice regular season coach but with the way he manages players and rotations i would be shocked if they win a title with Stevens at the helm.
He doesn't play guys big minutes in the regular season, but he absolutely does in the playoffs. We had 3 guys at ~36mpg in the playoffs last year, and Brown was at ~32mpg (likely would have been ~36mpg if he hadn't hurt his hamstring, he averaged just under 38mpg before the injury). Among our normal starters in last year's playoffs, we had plenty of 40+ minute games when we needed them. In the playoffs, Brad keeps a pretty tight rotation, and has not hesitated to play his studs big minutes when needed
I mean, I guess you could complain that he doesn't play our guys really big minutes in the regular season, but that should help us, not hurt us, when it comes to the playoffs. Brad has shown over the past couple of years that he will play his guys shorter minutes in the regular season to keep them fresher, and then takes off the leash when needed in the playoffs.
And sure, Brad will always throw out some odd lineups in November /December (like an IT/AB/Crowder/Gerald Green/Horford lineup - who the hell would play that lineup? It's obviously not going to work) before settling on a more rigid rotation, but those have ended up helping a ton later in the season when injuries pile up, or in the playoffs when we needed a change. Trying those lineups out during the unimportant games at the start of the year has ended up being immensely valuable to past couple of years