Championship or bust is an unfair standard. So many variables beyond the control of even the smartest NBA teams have to flip the right way to win four playoff series. The diciest one is health. The last team standing is usually among the healthiest. Maybe you can overcome an injury to a role player or two, but not a star.
Giant sports science staffs and fancy technology can maybe forestall the effects of age, or reduce the chances of suffering some particular wear and tear injury. They can't make collisions less violent, or prevent someone from landing on someone else's foot at the wrong time. Lots of championship-caliber teams never won championships.
So, yes, championship or bust is an unfair measure of success. It's also the cruel reality of making a trade like the Phoenix Suns did in reshaping the landscape of the league -- trading three very good support players (Mikal Bridges, Cameron Johnson and Jae Crowder, though Crowder of course was not playing for the Suns) and every unprotected draft asset available (four first-round picks, one swap) to the Brooklyn Nets for Kevin Durant and T.J. Warren.
Durant is one of the dozen greatest players ever, at worst. He has maybe been the league's best all-around player when healthy this season. Players like that rarely get traded, ever.