The WT book called True Peace and Security -From What Source? (copyright 1973) on page 86 in ph. 24 says: "In all the religions of Christendom, fewer young men are entering the seminaries, religious schools are closing their doors, and a great number of the religious magazines have ceased publication. The churches in general are finding their attendances growing smaller. Many church buildings are up for sale."
Something similar to that is now happening to the WT's JW religion. Years ago the WT stopped allowing JW's to have a subscription to the issues of the WT and the AW (I remember the WT cancelling my subscriptions to such), telling them instead to obtain them at the KH. Later the number of pages of WT issues per year were downsized and especially of the AW. KHs have been bought out by the WT (from the congregations) and a number of those have been sold off. In person face-to-face witnessing (especially door to door) by JWs has virtually ceased. A high percentage of young people raised in the JW religion do not believe in the religion (at least people on this site have said such). Meeting attendance in the KHs has virtually ceased, and there is evidence that attendance numbers in virtual meetings of the JW religion are likely overstated.
The WT claims that Christ is ruling as king and that JWs on Earth are subjects of that kingdom. As such, the WT claims that their JW religion is a part of Christ's kingdom, but claiming to be an earthly part of Christ's kingdom makes it a part of Christendom - by definition. The JW religion is going down with the rest (or at least most of the rest) of Christendom, as rapidly increasing numbers of people embrace irreligion and secularism.