The letter of Jude is a brief and powerful letter. When you read the letter, you notice the drive of a prophet. God’s Spirit has used Jude to describe the evil in Christianity and the judgment over it at the coming of the Lord Jesus in the forward-looking speech of the prophets.
The picture that you are presented here of Christianity is not directly a picture that makes you happy, but it is the reality. If you were withheld from that reality you would have missed the necessary warnings that should help you to acknowledge the attacks on God’s truth. But at the same time Jude encourages you. He actually points at the unfaltering faithfulness and omnipotence of God and the Lord Jesus to those who are willing to hold on to the truth that has been transmitted to them and to defend it against the attacks.
When you read this letter and compare it with chapter 2 of the second letter of Peter, then you see that certain issues occur in both letters. Still, these same issues are presented from a different point of view. Peter addresses Jewish Christians and speaks about sin and unrighteousness. Jude addresses all Christians and speaks about the apostasy of the Christian truth, the abandonment of the most holy faith.