This statement would be a good example of your opinion interjected into scripture.
4 For if God did not spare the angels who sinned, but cast them down to hell and delivered them into chains of darkness, to be reserved for judgment; 5 and did not spare the ancient world, but saved Noah, one of eight people, a preacher of righteousness, bringing in the flood on the world of the ungodly; 2 Peter 2:4-5
Peter associates these angels who sinned with the time of Noah, as He also does in 1 Peter 3.
19 by whom also He went and preached to the spirits in prison, who formerly were disobedient, when once the Divine longsuffering waited in the days of Noah, while the ark was being prepared, in which a few, that is, eight souls, were saved through water.
1 Peter 3:19-20
Jude associates the angels who sinned with the sexual immorality in Sodom.
6 And the angels who did not keep their proper domain, but left their own abode, He has reserved in everlasting chains under darkness for the judgment of the great day; 7 as Sodom and Gomorrah, and the cities around them in a similar manner to these, having given themselves over to sexual immorality and gone after strange flesh, are set forth as an example, suffering the vengeance of eternal fire.
Jude 6-7
Since there is no other angels who sinned in this manner, we know he is referring to the angels who sinned during the time of Noah, since he also quoted Enoch, it's a dead give a away what he is referring to in verse 6, since the book of Enoch is all about that event.
JLB
Man, everybody is going out of context today.
JudeNew American Standard Bible (NASB)
The Warnings of History to the Ungodly
1 Jude, a bond-servant of Jesus Christ, and brother of James,
To those who are the called, beloved in God the Father, and kept for Jesus Christ: 2 May mercy and peace and love be multiplied to you.
3 Beloved, while I was making every effort to write you about our common salvation, I felt the necessity to write to you appealing that you contend earnestly for the faith which was once for all handed down to the saints. 4 For certain persons have crept in unnoticed, those who were long beforehand marked out for this condemnation, ungodly persons who turn the grace of our God into licentiousness and deny our only Master and Lord, Jesus Christ.
5 Now I desire to remind you, though you know all things once for all, that the Lord, after saving a people out of the land of Egypt, subsequently destroyed those who did not believe. 6 And angels who did not keep their own domain, but abandoned their proper abode, He has kept in eternal bonds under darkness for the judgment of the great day, 7 just as Sodom and Gomorrah and the cities around them, since they in the same way as these indulged in gross immorality and went after strange flesh, are exhibited as an example in undergoing the punishment of eternal fire.
8 Yet in the same way these men, also by dreaming, defile the flesh, and reject authority, and revile angelic majesties. 9 But Michael the archangel, when he disputed with the devil and argued about the body of Moses, did not dare pronounce against him a railing judgment, but said, “The Lord rebuke you!” 10 But these men revile the things which they do not understand; and the things which they know by instinct, like unreasoning animals, by these things they are destroyed. 11 Woe to them! For they have gone the way of Cain, and for pay they have rushed headlong into the error of Balaam, and perished in the rebellion of Korah. 12 These are the men who are hidden reefs in your love feasts when they feast with you without fear, caring for themselves; clouds without water, carried along by winds; autumn trees without fruit, doubly dead, uprooted; 13 wild waves of the sea, casting up their own shame like foam; wandering stars, for whom the black darkness has been reserved forever.
(My thanks to the Bible Gateway where I copied.)
The angels spoken of here are in chains somewhere and I suggest to you that they are, what, not having fun? (Isa 14:12, Luke 10:18 & Rev 12:1-17)