The starting unit really is so much slower on offense, and Tim is a major part of that slowness. In situations that are not transitions, (i.e., when the other team has scored and we are coming up court in a normal offensive set), it takes a very long time for the players to get into their positions, particularly Tim. Secondly, because the Spursian "beautiful ball" scoring does not have a way of spotlighting Kawhi, and the team has been trying to spotlight Kawhi (to great effect for the scores, I might add), the ball movement of the last couple of years has given way to more iso plays for both Kawhi and Aldridge.
Both of those factors contribute to slow down of the offense. Moreover, when the Spurs set up their offense, everybody on the planet knows where TP is going to dribble, how the rest of the team is going to move while he dribbles, and where he is likeliest to pass the ball out of the dribble. This has been going on for at least the last two years, and as it gets worse, Tony has nowhere to go with the ball because every passing lane is cut off. So he dribbles and dribbles, looking for 'openings' and finding none.
It would be really nice to see some different offensive sets, but I don't know that that is going to happen. What makes us successful is that, even though we are slow and everyone knows what we are going to do, we still do it better than (almost) anyone else, and we wear teams down when our bench comes in with a frenetic pace and no set offensive sets, and it seems to work well in putting other teams on their heels.
If the starters did what the second team does it wouldn't work because they don't have the personnel for it, and because teams would adjust to what they do if it happened all the time.
I think the predictability (and pace) of the first team and the lack of predictability (and different pace) of the second team has been hugely successful for us in the regular season, but over a playoff series, that is a lot easier to figure out, and it will be considerably tougher to win. Hope we do, though.