No. That there are true believers inside of Roman Catholicism (Great Whore of Revelation 17 and Beast of the Sea of Revelation 13), or other fallen churches, doesn't make their systems of theology true. God winks at ignorance.
In Revelation 18 it is written:
Rev 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.
Rev 18:2 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.
Rev 18:3 For all nations have drunk of the wine of the wrath of her fornication, 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.
Rev 18:4 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.
Rev 18:5 For her sins have reached unto heaven, and God hath remembered her iniquities.
Therefore, God's people are indeed in the false system of Roman Catholicism, and her harlot daughters (Revelation 17), but
they are to be called out of those false systems into the (singular) true church, as identified in Revelation 12. It is
not a
'nebulous everywhere and nowhere'. The true church, has order, structure, offices, functions, and gifts as seen in Acts 6:3, Acts 15, 1 Corinthians 12-14; Ephesians 4-5 and elsewhere.
Scripture, as already spoken of in Revelation 12, and elsewhere, tells how to identify the true church. If you think that the true church is 'a nebulous everywhere and nowhere' membership, you have left the pattern given and are not in the true church, even if you are a believer.
In fact the true church is found in the Sanctuary (Psalms 77:13), as each phase of the sanctuary shows the movement and characteristics of the true church.
Outer court - Ezekiel 10:5
Holy Place - Exodus 26:33
Most Holy Place- Exodus 26:33
As there are 3 places. There are 3 phases of the true church.
Adam unto Moses and Israel
(Israelites) was the first Outer Court Phase -
Acts 7:38 This is he, that was in the church in the wilderness with the angel which spake to him in the mount Sina, and with our fathers: who received the lively oracles to give unto us:
The Disciples and Apostles of Jesus Christ moved by faith into the Holy Place, and became the next phase -
Act 2:1 And when the day of Pentecost was fully come, they were all with one accord in one place.
Act 2:2 And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting.
Act 2:3 And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
Act 2:4 And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
Act 2:33 Therefore being by the right hand of God exalted, and having received of the Father the promise of the Holy Ghost, he hath shed forth this, which ye now see and hear.
Psa 133:1 A Song of degrees of David. Behold, how good and how pleasant it is for brethren to dwell together in unity!
Psa 133:2 It is like the precious ointment upon the head, that ran down upon the beard, even Aaron's beard: that went down to the skirts of his garments;
Psa 133:3 As the dew of Hermon, and as the dew that descended upon the mountains of Zion: for there the LORD commanded the blessing, even life for evermore.
Act_10:45 And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.
Act_11:15 And as I began to speak, the Holy Ghost fell on them, as on us at the beginning.
Rev 5:6 And I beheld, and, lo, in the midst of the throne and of the four beasts, and in the midst of the elders, stood a Lamb as it had been slain, having seven horns and seven eyes, which are the seven Spirits of God sent forth into all the earth.
They received a new name:
Act_11:26 And when he had found him, he brought him unto Antioch. And it came to pass, that a whole year they assembled themselves with the church, and taught much people. And the disciples were called Christians first in Antioch.
The third phase, is easily identified after that and a new name.