it may sound reductionist but Depth is the theme of this postseason so far. The teams that are extremely thin with their lineups are getting exposed.
Teams like the Twolves, Clips, Knicks have been getting huge minutes from their 3rd/4th options and sixth men off the bench and are succeeding.
You always needed at least a 7-8 man rotation to win in postseason. Whether it's 40 years ago 10 years ago or now.
Pick any championship team and you'll see somebody off the bench had to be decent who knew their role and did exactly what they were asked to do. Super teams can work if the bench is alright. Miami Big Three, an obvious super team, remember they had a couple decent names off the bench such as Shane Battier, Mike Miller, even Haslem being OK off the bench. Then later adding Ray Allen.
The problem with a team like Suns is that their big three doesn't work together like that. They got no elite playmaker, just three scorers taking turns on offense, no defense besides KD ina few situations. And their big man rotation is mid. While the Miami big 3, all of them were capable of playing defense and getting buckets.