The NBA D-League in the past has been a shallow, sorry excuse for a minor league farm system. Today, it’s a little bit different, and more expanded, but still, it’s not at the extent of minor league systems that other pro sports have.
Take, for example, the minor league system for the MLB. In the MLB, most teams have an affiliation with a minor league team (if not more than one) and the system is deep enough for there to be multiple levels for players to move up in the rankings. The entire system consists of 240 teams altogether.