Hard to improve on that. That's the bottom line. Unless LMA is showing signs that he's going to pout away a whole season, there's no good reason for the Spurs to do this. They sure as won't get better right away. And only a quality first-round pick plus a decent young player could make them better in the medium term.
If the Spurs had moved him in the offseason, and then tanked to get two lottery picks? yeah, build that future. But getting two first round picks over 30 (even 25) isn't going get it done. And neither is getting someone else's cast-off, over-paid, mid-tier player.