To which I left the following comment (slightly edited):
I think you are mistaken to take comfort in Belloc's words.
I see nothing at all to suggest that the Roman Catholic Church is, in any way, immune to the convergence, hollowing-out, "skin-suit" fate of all the other large Western institutions. Its trajectory is identical with that of - say - Oxford University, which is also very long-lived (nearly 1000 years) and of unsurpassed reputation in scholarship over many centuries; and yet has (with remarkable swiftness and completeness) become an academy of lies and evil.
Of course, your confidence that the RCC will last 'forever' (i.e. last as a faithful church and not as merely a mask for totalitarian materialism) is actually rooted in your assumptions, and not in evidence; yet most people would regard the scriptural/ theological/ traditional grounds for these assumptions as both slender and ambivalent*.
In sum, it would be a stronger position for the RCC if those (many) real Christians who are yet present in it, would regard the true church as something vulnerable to human corruption.
If that church is to be saved from becoming assimilated to the demonic agenda of the globalist totalitarians, it will need members to locate the true church in their own hearts (in communion with the Holy Ghost) rather than somewhere present in the increasingly corrupted bureaucracy.
(Recall how the actual RCC abandoned centuries of dogma and theology almost overnight in 2020; when the church willingly, enthusiastically agreed to its own closure for an undefined time period - which in practice for many people lasted many months during which there were no sacraments. Lourdes - the premier place of spiritual healing - was actually Closed... Just think what That implies about the RCC.)
If the true and mystical church is located somewhere in the actual institution of the RCC, it will still require personal discernment to find that mystical-true church, among the great outnumbering mass of fifth-columnists, demonic servants, and time-servers.
* For example (especially), in that most-unreliable (IMO) of Gospels, Matthew 16:8 - And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it. Such a phrase (no matter how often repeated) is awfully little upon-which to hang one's absolute faith in what is already (and increasingly) a top-down-implemented and actively-evil material institution.