The word "Corban" can be opaque to a modern reader. Mark explains it as a gift devoted to God. Jesus uses the practice as an example of how a religious tradition could be invoked in a way that undermined a command of God.
The controversy is especially pointed because it concerns responsibility toward father and mother.
Vows and dedications were serious religious acts. Declaring property dedicated to God could place it under a religious obligation. In the dispute reported by the Gospels, Jesus objects to a use of such dedication that allowed a person to withhold resources that otherwise could have supported parents.
The point is not that gifts to God were inherently wrong. Jesus' criticism is directed at a tradition's practical effect when it is allowed to override the command to honor one's parents.
Knowing what "Corban" means turns an unfamiliar foreign word into a concrete ethical conflict. A practice that sounded especially religious could become a means of avoiding an ordinary but demanding duty.
Jesus therefore exposes a recurring danger: religious language can be used to justify disobedience rather than faithfulness. The passage contrasts outwardly pious dedication with the tangible responsibility owed to one's family.