When Jorge Mario Bergoglio chose the name Francis for his papacy, he was asking Catholics to make a connection to the medieval religious revolutionary Francis of Assisi. Early in his spiritual pilgrimage, the original Francis heard the icon of the crucified Christ in the Italian church of San Damiano speak to him. It said “Francis, Francis, go and repair My house which, as you can see, is falling into ruins.”

When the pope arrives in Ireland this weekend, he will find a Catholic church not just falling to ruin, but in some respects beyond repair. He will be greeted with joy by the faithful, but few, even among them, will expect him to be able to fix an institution that has been shaken to its very foundations.

On the face of it, it is strange to think that, when Francis touches down on Irish soil, it will be only the second time a serving pope has visited the island. But popes didn’t visit Ireland because they didn’t have to. After partition and the foundation of an independent Irish state in 1922, there was nowhere more securely Catholic. Well over 90% of the population belonged to the faith, and even more remarkably almost all the Catholics were practising. The church controlled most schools and hospitals. Governments obeyed it, banning divorce, contraceptives, abortion and “dirty” books (including the bulk of modern Irish literature). A pope visiting Ireland would have been the very definition of preaching to the converted.

As a child I served mass most days in the church near our council housing estate in west Dublin. It has a vast open interior with soaring ceilings, three altars and row after row of long wooden seating. On Sundays there were six masses, on the hour from seven to noon. Every one of them was full or close to it. There were, at any given time, seven or eight priests to say them. They were busy: during the week, there were morning masses, evening devotions, sodalities, weddings, funerals and confessions. The church was as familiar to most of us as our own homes.

And now? There is one priest holding things together on his own. The church itself is like a suit made for a very fat man who has now slimmed down to a fraction of his old weight. The rows are almost all empty, even for Sunday mass. The soaring ceilings merely echo the emptiness. The place is cold in winter because the parish can’t afford to heat it, and there is no longer the warmth of crowded bodies. The remaining faithful are almost all older and female.

Souvenir figures of Pope Francis on sale in Ireland. The pope is due to visit this weekend. Photograph: Clodagh Kilcoyne/Reuters

It’s not like this everywhere in Ireland. Rural parishes are generally more vigorous, even if many of them now have African priests, reversing generations of missionary effort. Some middle-class suburbs still have well-resourced and well-attended churches. The church itself retains a stranglehold on the system of primary education and a huge influence in healthcare. But the decline is still stark: from a weekly mass attendance of over 80% in 1979, when John Paul II made the only previous papal visit, to about 35% now. And with it has come a loss of political power crystallised in the overwhelming vote in May to remove the constitutional ban on abortion.

Some of this decline would have happened anyway. The sheer dominance of the Irish Catholic church was not normal. It happened because resistance to the Reformation had been the most effective way for most of the indigenous population to resist assimilation into British power, which was, of course, defined by Protestantism. With the decline of the Irish language in the 19th century, Catholicism became an even stronger marker of distinctive identity. Mass emigration made the universal and international nature of the church even more comforting – if you had to go from Connemara to Connecticut or from Cavan to Coventry, at least the mass was still the same, and the priest was probably still Irish. And then the partition of Ireland in 1921 created two religious ghettoes, the “Protestant state for a Protestant people” in the north mirrored by its Catholic counterpart in the south. Dissident minorities could be easily cowed on both sides of the border.

This was never going to last. The belated modernisation of the Irish economy from the 1960s onwards gradually created an urbanised, secularised and much more highly educated society. Feminism put down deep roots. A patriarchal, authoritarian institution reliant on blind faith and the power of conformity was never going to survive these processes intact. Indeed, the Irish Catholic church was all the more vulnerable precisely because its power had gone largely unchallenged. Like a child raised in a sterile environment, its immune system was weak.

But what might have happened slowly and gently, with half the population remaining faithful and half slipping into benign indifference, has instead happened quickly and bitterly. Buddhist monks in Vietnam used to set themselves on fire – the Irish bishops and cardinals have done so metaphorically, but no less shockingly. The petrol they poured over themselves was what Francis, in his open letter released on Monday, called “atrocities perpetrated by consecrated persons”. The flame they set to it was the systematic covering up and effective facilitation of the sexual abuse of children by clergy.

Perhaps some radically different Catholicism will emerge in time, stripped of patriarchy and authoritarianism

While this horror story began to be told in the 1990s, it has since been compounded by three factors. First, child abuse by priests in parishes is just one part of a wider story of institutional abuse in which women and children were incarcerated in industrial schools, Magdalene laundries and mother-and-baby homes. This still emerging story casts a sickly retrospective glow on Holy Catholic Ireland – it is ever clearer that it maintained its “purity” through systematic terror.

Second, what many Irish Catholics thought was a local problem, created by a few evil priests and weak bishops, has turned out to be an international phenomenon, and thus implicit in the nature of the institutional church itself. This was a global cover-up directed from the Vatican.

Third, the Vatican’s response has been pitiful. In a special letter to Irish Catholics in 2010, the then Pope Benedict expressed “shame and remorse”, and claimed to share their “dismay and … sense of betrayal”. But that simply means that when Francis now says the same things, their effect is blunted. The fine words have not been matched by real change. The brilliantly articulate Irish abuse survivor Marie Collins agreed to serve on the Papal Commission for the Protection of Minors established by the Vatican in 2014. But she resigned over its lack of real clout within the church.

And it’s too late now to offer more apologies and promises. Francis seems a fine person, and most Irish people will be glad to see him. For the remaining faithful his presence will bring pleasure and comfort. But the model Catholic state that Ireland once was is in the tomb, and there will be no resurrection. Perhaps something else will emerge in time, some radically different version of Catholicism, stripped of patriarchy, authoritarianism and institutional self-regard. In the meantime, there is only one sermon that can be truthfully preached in the ruined Irish church: absolute power corrupts absolutely.

• Fintan O’Toole is a columnist with the Irish Times