Not exactly true when it comes to Popovich. Perhaps at first he leaned in the direction of adapting more to his players, but at the same time he slowly implemented his system, little by little. He also had a very talented roster which made things easier. Over time the Spurs became more about the system than the players, which I think is a good thing, but that took time. Now the Spurs bring in players specifically suited to fit in that system and it's a win-win for everybody, it makes the team better and it makes the players look better.
I would say that the Warriors are getting to that point as well. They will never be able to keep all of their good players for salary cap reasons, but many of those players will be replaceable because of the system. Look at our great Kings teams years ago, we were able to bring in players that weren't even in the league anymore and they contributed because they happen to fit our system.
The problem the Kings have now is that they won't commit to one coach and one system and we have a hodgepodge of players who don't fit together or who fit a single system. This team has to choose, we set up a team around guys like Rondo, Gay, and Cousins and we play slow or we get rid of them all and play fast, you can't have it both ways. This offseason the choice must be made, if we keep Cousins we pick one style of coach, if we trade Cousins we pick another style of coach, but the two must be consistent.