This was basically their teaching on the dragnet parable.
https://wol.jw.org/en/wol/pc/r1/lp-e/2008523/0/0
12 In the centuries after the apostles left the scene, there continued to be some Christians striving to find and hold to divine truth. At least some of these had God’s approval, and he anointed them with holy spirit. Still, the death of the apostles removed a restraining influence, allowing a widespread apostasy to develop. (2 Thessalonians 2:7, 8) An organization grew up that unworthily professed to be God’s congregation. It falsely claimed to be the holy nation anointed with God’s spirit to rule with Jesus.
13. Why can it be said that Christendom had a role in the dragnet operation?
13 Do you think that unfaithful professors of Christianity had any part in the illustration of the dragnet? Well, there is reason to answer, yes, they did. The symbolic dragnet included Christendom. True, for ages the Catholic Church tried to keep the Bible from the common people. Nevertheless, over the centuries members of Christendom played a key role in translating, copying, and distributing God’s Word. Churches later formed or supported Bible societies, which rendered the Bible into the languages of remote lands. They also sent out medical missionaries and teachers, who made rice Christians. This gathered vast numbers of unsuitable fish, who did not have God’s approval. But at least it exposed millions of non-Christians to the Bible and to a form of Christianity, although corrupted.
14. How was fishing for fine fish aided by some work done by the churches of Christendom?
14 All the while, the scattered faithful ones adhering to God’s Word exerted themselves as best they could. At any given time, they constituted God’s true anointed congregation on earth. And we may be sure that they too were catching fish, or men, many of whom God would view as fine and whom he would anoint with his spirit. (Romans 8:14-17) These fine professors of Christianity were able to bring Bible truth to many who had become rice Christians or who had gained limited Biblical knowledge from the Scriptures translated into their tongues by Christendom’s Bible societies. True, the collecting of fine fish was going on, even though most being gathered by Christendom were unsuitable from God’s standpoint.
15. Pointedly, what is represented by the dragnet of the parable?
15 So the dragnet represents an earthly instrument that professes to be God’s congregation and that gathers in fish. It has included both Christendom and the congregation of anointed Christians, the latter having continued to collect fine fish, under the invisible guidance of the angels, in line with Matthew 13:49.