Few sights of man-made things have instilled as much awe in me as La Basilica Di San Pietro and most of them are also in Rome (namely the Pantheon and Moses @ Basilica di San Pietro in Vincoli).
But to me, despite all of this, there was a lot of sadness in that experience - because you know how desperately poor common folks were, how instead of building such status mega symbol they could have done some proper good. But not for church of that era, it was busy fighting for power and money of that world and trying to show how above everybody else they were.
You can see miniature scale of this in literally every (also non-) older European village or town - religious buildings have received by far the most funding and care, sometimes overshadowing kings castles themselves. Cathedrals were always built to impress masses, and this one is just on top of the game, by huge margin for good reasons I believe.
This is a tired caricature. We live in comfortable times. Materially, in many way, we are much more comfortable today than kings were back then. The world was different then, and it is irresponsible to project anachronistic categories onto a period of history that operated differently. And that somehow there exists a conflict between building magnificent churches and dealing with poverty is simply nonsense (indeed, poverty was dealt with through tithing and donations and by convents and monasteries with that charism; the first hospitals, for example, were founded by nuns, hence why in many languages the word for nurse is still "sister"). You can do both, hence the corporal works of mercy and spiritual works of mercy. Magnificent churches were not somehow the private property of some caricaturish class of clerical villains (who had no heirs, legitimate ones, anyway). They were the common patrimony of the Church. They were often constructed over long periods of time by the people in the community. They gave everyone, especially the poor, the possibility of witnessing and experiencing beautiful art and architecture that might otherwise only be accessible to the very richest of the magnates (and I challenge you to find a magnate who owned anything as spectacular as St. Peter's).
(Even today, you hear people ask the silly question "why doesn't the Church sell all its artwork and give the money to the poor?". If you allow that question to sink in for a moment, it becomes clear how preposterously silly it is to ask it. So you sell it. Then what? Now, these artworks are the property of private collectors or state institutions. Is that what you want? And the money: you think that will somehow "end poverty"? After food is digested, one's hunger returns. Far greater sums have been expended on the poor. The poor will always be with us. It is something we must continuously deal with. Robbing them of access to beautiful artwork, and depriving the Catholic faithful of their patrimony, is a pretty shitty solution, if it can even be called that.)
Frankly, what I find shameful is that we are richer than we're ever been, and yet we can't seem to produce anything that approaches the beauty of these old cathedrals. We have monks in Wyoming who are using CNC stone carving to build a gothic monastery[0], for crying out loud! We've never been in a better position to build beautiful things and cheaply at scale. And that's kind of the message of these buildings. It's not the material wealth per se, but the magnanimity of spirit that made this beauty possible and the spiritual awe it continues to inspire to this day. It's a condemnation of our vulgarity, of our consumerism. Even the churches we build today usually look like shit. If that's not cultural decadence, I don't know what is.