I think he failed to mention the real reason, coaching. The NBA in all honesty does not have a ton of great coaches. Probably nearly half the league, if not more, is filled with coaches who simply aren't ready to be head coaches (younger guys) or coaches who just aren't skilled and knowledgeable enough (older coaches). A lot of coaches don't know how to put their players in the best position for them to succeed.
Look at the bottom three teams. Spurs, Mavericks, Rockets, Bucks, and Pistons. Spurs have Poppovich, Mavericks have Carsisle and had Avery Johnson and Don Nelson. Rockets have McHale, but had Rick Adelman, Jeff Van Gundy, and Rudy Tomjanovich. All great coaches who knew how to juggle playing their systems, but also integrating different players into it and still getting the most out of them.