Great Babylon of the Apocalypse is the confusion of voices. It is the divided church, squabbling, making merchandise of the saints and of religion. It is the divisional denominational system that has the unbelievers so mixed up that they wonder who they should believe.

Babylon has come into existence from man-made forms, rituals, and governments--church orders that in no way reflect the orders that are established in Scripture. How many 1 Corinthians 14 church services have you been in?  Instead of multiple elders, co-equal, who shepherd the flock, and deacons, we see ministries that lift up men (and women) so Christ is not the one who gets the glory.  We see organizations and persons and doctrines idolized in spiritual fornication.  The humility that was in the apostolic office is gone from these organizations.  Rather than one unified voice of a Spirit-led, Spirit-powered Church, we have thousands of voices of rationalized dogmas and fights over turf and competitiveness.  This is Babylon.

Here is just one example clipped from a news article: "All references to marriage and chastity are gone, along with the language about refusal to repent of sin. The new language speaks instead of submission to the Lordship of Christ and being guided by Scripture and confessions. In any other context, that language might not seem revolutionary, but in this case, it means the denomination's surrender to those pushing for the normalization of homosexuality."  source

Jesus prayed that we would all be one, but we need to become one with the Father and the Son before we can ever become one with each other.  Ephesians 4 shows how we will become one, and it won't be by any ecumenical movement.  Jesus prayed that we become one so that the world would believe.  When we become one, the world will believe.

Revelation 18  
1 And after these things I saw another angel come down from heaven, having great power; and the earth was lightened with his glory.  
2 And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.  
3 For all nations have drunk of the wine of the wrath of her fornication [speaks of idolatry], and the kings of the earth have committed fornication with her, and the merchants of the earth are waxed rich through the abundance of her delicacies.  
4 And I heard another voice from heaven, saying, Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues.  
5 For her sins have reached to heaven, and God hath remembered her iniquities.  
6 Reward her even as she rewarded you, and double to her double according to her works: in the cup which she hath filled fill to her double.  
7 How much she hath glorified herself, and lived deliciously, so much torment and sorrow give her: for she saith in her heart, I sit a queen, and am no widow, and shall see no sorrow.  
8 Therefore shall her plagues come in one day, death, and mourning, and famine; and she shall be utterly burned with fire: for strong is the Lord God who judgeth her.  
9 And the kings of the earth, who have committed fornication and lived deliciously with her, shall bewail her, and lament for her, when they shall see the smoke of her burning,  
10 Standing afar off for the fear of her torment, saying, Alas, alas that great city Babylon, that mighty city! for in one hour is thy judgment come.  
11 And the merchants of the earth shall weep and mourn over her; for no man buyeth their merchandise any more:  
12 The merchandise of gold, and silver, and precious stones, and of pearls, and fine linen, and purple, and silk, and scarlet, and all thyine wood, and all manner vessels of ivory, and all manner vessels of most precious wood, and of brass, and iron, and marble,  
13 And cinnamon, and odours, and ointments, and frankincense, and wine, and oil, and fine flour, and wheat, and beasts, and sheep, and horses, and chariots, and slaves, and souls of men.  
14 And the fruits that thy soul lusted after are departed from thee, and all things which were dainty and goodly are departed from thee, and thou shalt find them no more at all.  
15 The merchants of these things, which were made rich by her, shall stand afar off for the fear of her torment, weeping and wailing,  
16 And saying, Alas, alas that great city, that was clothed in fine linen, and purple, and scarlet, and decked with gold, and precious stones, and pearls!  
17 For in one hour so great riches is come to nought. And every shipmaster, and all the company in ships, and sailors, and as many as trade by sea, stood afar off,  
18 And cried when they saw the smoke of her burning, saying, What city is like to this great city!  
19 And they cast dust on their heads, and cried, weeping and wailing, saying, Alas, alas that great city, wherein were made rich all that had ships in the sea by reason of her costliness! for in one hour is she made desolate.  
20 Rejoice over her, thou heaven, and ye holy apostles and prophets; for God hath avenged you on her.  
21 And a mighty angel took up a stone like a great millstone, and cast it into the sea, saying, Thus with violence shall that great city Babylon be thrown down, and shall be found no more at all.  
22 And the voice of harpers, and musicians, and of pipers, and trumpeters, shall be heard no more at all in thee; and no craftsman, of whatsoever craft he be, shall be found any more in thee; and the sound of a millstone shall be heard no more at all in thee;  
23 And the light of a candle shall shine no more at all in thee; and the voice of the bridegroom and of the bride shall be heard no more at all in thee: for thy merchants were the great men of the earth; for by thy sorceries were all nations deceived.  
24 And in her was found the blood of prophets, and of saints, and of all that were slain upon the earth.