The Old Testament Law and Covenant were good, as the Scriptures testify. Yet, many a person in the Old Testament abused the good revelation of God to Moses on Sinai for their own means and ends. Numerous books of the Prophets clearly address this issue.
Sometimes the trappings of the Kingdom of Heaven are misused to construct an empire dedicated to oneself (or a group).
One of the reasons the Pharisees rejected their Messiah, Jesus, was precisely due to this. Using the trappings of the Law, they built for themselves a place of power and control over others. They built for themselves a place of influence and prestige. They had constructed their own little empire. For them, the Law was not so much a life-giving revelation as it was a tool by which they could lord it over others and bring them into submission. Their empire was of greater value to them than the Kingdom of Heaven.