‘And his brothers went to feed their father's flock in Shechem.'
Over the years things and circumstances change. It may be that Joseph was now not sent with them because of how they felt about him, but it is equally likely that he was kept at home simply because of his father's needs (he was ‘the son of his old age') and possibly even for the very purpose of maintaining communication between home and herd. Jacob, as is the case with those who show favouritism, does not appear to be aware of how much Joseph was hated. He thought Joseph was wonderful and assumed everyone else did as well.
It is clear that any unpleasantness resulting from previous happenings at Shechem (Genesis 34) is now forgotten. It may well be that the inhabitants were just unaware of the connection of the brothers with the previous incident and they appeared peaceable enough now. Most eyewitnesses were dead or had been absorbed into the family tribe.
The land at Shechem was clearly good pasture for there is now no suggestion of separation of the flocks. Perhaps famine or raids by bandits had diminished them. There were many ups and downs in life at that time. Or perhaps Shechem was seen as fertile enough for all.