They are missing a system where Kawhi is dangerous enough that him existing creates the initial mismatches that lead to multiple players scoring, even if he doesn't touch the ball.
Right now, the Spurs' offense as it relates to Kawhi just doesn't have that organization. A lot of that has to do with the fact Kawhi's best two-point element is playing in the post, and that's a lot less predictable than penetration is. It's hard to run post-up oriented set plays for guys other than the post player. Sure, you have the hammer that comes from the post (the Diaw special), but that's just one play that has to be used sparingly to maintain its effectiveness. It's like the four-down Duncan era, but a not-as-good version and in a league that can handle post-up wings for the most part. The diversity relies on guys making cut-throughs and teams doubling, which as discussed before is unpredictable, as the help can come from multiple places. Of course, you also have Kawhi's three-point game, but unless they start putting in Korver-inspired sets for Leonard, that's not good enough.
I can't tell you what type of sets the Spurs can use to get that type of effect out of Kawhi. And that's the main reason why I've been apprehensive about wing-oriented offenses. They're just clunky, because the wing will either have to play like a PG or like a PF. With the Korver/Allen set excluded, wing-led offenses are only about individual talent and the mismatches that talent can create. Unless Kawhi becomes a guy who can drop 30-33ppg if the defense doesn't commit to stopping him, that system won't work as well as the systems for guys like James and Durant have.
At least there's still LMA to help balance things out.