What does Luke 17:27 mean?

Worldly culture will be shocked and surprised at the second coming of Jesus Christ. In the time of Noah, people practiced horrific evil but still celebrated normal things like marriage. They had no concept of imminent judgment. Before Jesus returns, the conditions of the earth will be horrific thanks to the tribulation; some will still manage to make money and live luxuriously.

All the activities mentioned here are celebratory. What the reference to Noah adds is "that the wickedness of man was great in the earth, and that every intention of the thoughts of his heart was only evil continually" (Genesis 6:5). Noah was God's "herald of righteousness" (2 Peter 2:5) and in his obedience to God, he "condemned the world" (Hebrews 11:7). That is, by obeying God, He showed that having faith in God was possible, even in such an extremely sinful culture (Psalm 23:5).

As in the time of Noah, God will send warning witnesses to the people of the Babylon of the tribulation: the 144,000 (Revelation 7:1–8) and the two witnesses whose deaths the people will celebrate (Revelation 11:1–13). The people will intentionally reject God and devote themselves to licentious living and worldly treasures. Yet their judgment will be far more terrible. They will experience God's wrath in the seven seal judgments, seven trumpet judgments, and seven bowl judgments. Babylon, the economic system they love, will not be destroyed by a flood; it will be burned with fire (Revelation 18).

Matthew 24:38–39 gives the same warning but says they will be unaware of their impending judgment. How can this be? Jesus' prophecy may be referring to people who ignore the warnings of the two prophets. He may be referring to a time right before the judgments begin. Or it may be that even while the world suffers cataclysmic damage, there will be some with the money and resources to think they're untouchable. After the sixth trumpet judgment, Revelation 9:20–21 describes, "the rest of mankind, who were not killed by these plagues, did not repent of the works of their hands nor give up worshiping demons and idols of gold and silver and bronze and stone and wood, which cannot see or hear or walk, nor did they repent of their murders or their sorceries or their sexual immorality or their thefts." What we've seen throughout history certainly demonstrates mankind's capacity to live in heinous sin while ignoring warning signs.