Coaches can't win with substitution patterns. If they follow the clock the same way every game, fans complain that they don't allow a group that's working well together to say on the floor. If they respond to the particular dynamics of each individual game, fans complain that the players can't be consistent when their minutes keep fluctuating. If they employ a hybrid strategy, fans blame losses on poor substitution decisions.
Gentry's substitutions are fine. Once in a while it's possible to identify a mistake in hindsight, but that's because his players aren't very good and he has no way of predicting when someone is going to provide productive minutes and when they aren't.