The family is dysfunctional to the point they are blind to their own sin. This leads to self-righteousness.
Shechem is a place of danger (Gen. 34 in the name of justice some of the brothers committed great violence. Despite this Jacob sent Joseph to check on his siblings.
Looking at the big picture we can see God's hand in the timing of seemingly random actions.
The robe and dreams trigger brothers to want to murder him. They have an obsessive hatred. Reuben does show a small sign of humanity and the others agree to his suggestion out of a depraved satisfaction of Joseph suffering a slow death.
After Joseph is sold Reuben shows remorse but quickly goes along with the others. Evil will never be conquered with feeble actions. If it isn't exposed it will carry on.
The siblings leave Jacob believing his son was torn to pieces and they hypocritically comfort him.
Joseph in the pit signifies the loss of every earthly thing he relied on for security. (We live our lives to promote security for ourselves.) Joseph may believe his dreams were a lie and doubted God was with him. There is more to the pit than darkness: a call to a deeper reliance on God.