Sometimes 3rd options turn into 1st options depending on the situation/matchup, etc.
Kawhi has to carry a HUGE load on defense. Tony being able to relieve him at times is big advantage to not only him but the team.
I'm not sure what you want? Ever since the Big 3 era, there's times when the star player (Duncan in the past) will get limited shot attempts/touches. If you think the Spurs can win a championship with predictable like force feeding Kawhi in the post or just throwing the ball to him to go one-on-one, you're living in fantasy land. Kawhi isn't Kevin Durant, Lebron James, prime Kobe Bryant, etc. He's indeed a good all around offensive player right now, but he isn't someone who can win a duel with Curry like those players could, no matter the touches.
I see a matchup with Golden State going like this:
- Kawhi loses the scoring duel with Curry.
- LMA (hopefully) equalizes Thompson.
- Duncan probably loses his duel with Green.
So where's that extra scoring punch going to come from? Manu is too inconsistent at his age and miles to count on 15ppg+. Role players? They got good role players, too. Tony has to be that guy who can potentially go off for 25 points in a key game and average 15-17ppg over the series.