
Outside of superstars and stars, big SF's/combo forwards, who are at least competent at 3 and D, are the most coveted assets in the league. Most teams are trying to load up with as many as possible, so they can play 3 at a time for significant stretches.
Their value lies in being able to offer enough of what bigs and guards generally excel at, without the inherent limitations they generally possess.
It's only the archaic types, like the Spurs, who don't seem to place a premium on them.
This is the worst kind of roster construction in the modern NBA: Antiquated stars, small guards, slow bigs and severely limited lineup flexibility/versatility. They're basically what the Raptors were, only in a deeper conference. What's worse, they gave the Raptors the an hesis of this and did so without making them feel any pain (Anunoby, Mills in place of Green, looser protection on pick).