The Spurs are above-average at drafting, pretty elite by most accounts, so building through the draft is less of a "luck" plan and more of a developmental one (well, as much as the draft can be predicted/analyzed anyways I guess, there's always gonna be a Fultz or Darko in most drafts) for them. And again, the current roster is much closer to joining the tank race after the AS-break than it is to fighting for a play-in anyways, so barring a miraculous jump from one of our youngings, we probably won't have to depend on "getting lucky around the 7-13 seed".
My quarrel is exactly with the mentality in your second sentence, about seeing the draft as a "passive" approach that's somehow inherently worse than an "active" approach would be. Look how most trade-hungry teams and FOs end up; the Morey Rockettes, the Ainge Celtics, the Presti Thunder... All end up imploding and over-trading their way into corners. Not saying the Spurs would be like that in this case, just saying it's disingenuous to look down on drafting as a strategy for success, especially considering SanAn's market and ability to attract FOs.
If we were Miami, I'd go "yeah sure, get Simmons and some other stars will want to join him, the pieces will fall into place for us". But it isn't. The uncertainty of the draft is a necessary evil for small market, star-deprived teams. And as I told the other poster, it's not like Simmons alone will get the Spurs anywhere but the mediocrity we've finally escaped this off-season, so given we lack other tradeable assets beyond our picks (and it'd be superbly dumb of the FO to mortgage our own picks on an unproven core), I don't see Simmons in SanAn as a positive for anyone involved.