Cable pullovers allow for a great stretch and full contraction of the lats. The added benefit of having your entire back supported by lying on the ground lets you focus on volume without the fatigue accrued by supporting yourself.
Remember, big lifts first, then do this low-stress finisher for added volume.
Hating on CrossFit is trendier than those hipster Ray-Bans your aunt bought you. There are some aspects of CrossFit that deserve your attention, however.