Pitting playing time vs. practice is a false argument. Basketball is a culture that encompasses both, and each player is a mixture of talent and confidence. The latter of those two maximizes the former, and sometimes the talent level demands playing time because of the confidence level that is apparent in the player.
These dynamics play out in both practice and games, and no matter how many of the players on the roster happen to be displaying talent-maximizing confidence, every coach is still limited to 5 players at a time and 240 minutes total. So intuition is required, which is informed by being involved in practices and games. Fans second guess that understanding and those choices all the time, but it is always from a position of ignorance. Even practice film and/or transcripts would not help a fan understand more than a coach.
Even after all of the evaluation and scheme implementation, some of the stardom and contract negotiation is still subject to factors like timing, fit, and opportunity. Many players are stuck on teams that they don't have the right playing chemistry with, and others who have loads of that chemistry but do not properly shunt their own play to accommodate their teammates because of ego or personality. Some players are talented, but simply cannot play unselfishly, and others have difficulty communicating to teammates and/or coaches. The factors involved here are myriad and complex.
Isaiah Thomas should have been on the Dream Team, but personality conflicts dictated otherwise. Shaq should have been on that team also, but politics and need dictated otherwise. The opportunity is past, but the result is not necissarily what it could have been.
Rony Seikaly would have been a major talent upgrade at the center position for the Jazz, but he didnt want to come here. That choice affected the Jazz' championship hopes and also his own.
So opportunity is always subject to multiple factors, and history bears out those who take advantage of the opportunites that they are given, and sometimes they are unfair. But I find it much more compelling to discus the factors in play than to rank their importance. It is all important because it is all basketball.