The above statement reflects the freedom that the family felt after Gregor died.
Due to Gregor's condition, the family was forced to sell off things and find work to earn money for their daily living. They had to take care of Gregor and they felt trapped by him. They wanted Gregor to leave and free them to live their lives the way they wanted to. When Gregor died, they got their wish. Their disregard of Gregor was evident when the cleaning lady was the one who buried Gregor's remains.