Thank you for the compliment. Fortunately (?) I have a wife and children to remind me what little I know.
Having read the document, I can see your point. Clearly, Pius XI is speaking out against unity for unity’s sake. He is also speaking out against a “federation” of Christians, where there is no leader, a pan-Christianity.
Where we diverge, is in what gravity we apply to the prayer “event.” In my opinion, each man making his own appeal to the Father is a good thing. Should there been some other “global church” thing, that would have been a problem.
By inviting non-Catholics to Rome, I think Pope Francis is following the spirit of Pius XI, and going one step further, inviting them.
“You, Venerable Brethren, understand how much this question is in Our mind, and We desire that Our children should also know, not only those who belong to the Catholic community, but also those who are separated from Us: if these latter humbly beg light from heaven, there is no doubt but that they will recognize the one true Church of Jesus Christ and will, at last, enter it, being united with us in perfect charity.”
By inviting non-Catholics to Rome, I think Pope Francis is following the spirit of Pius XI, and going one step further, inviting them.
Matthew 4:8-9
Again, the devil took him to a very high mountain and showed him all the kingdoms of the world and their splendor.
“All this I will give you,” he said, “if you will bow down and worship me.”
But "the one step further" is the rub! This is not what Pius XI is suggesting at all. Pius XI just wrote a whole encyclical explaining what does not equate to religious unity. It spends the whole time explaining that it is only found in the Catholic Church. Nowhere does he suggest that Catholics should pray with non-Catholics in order to help this recognition along. That's because that would have gone against Catholic teaching. He knew that.
Francis has gone one step further: he promotes prayer with non-Catholics which goes against Traditional Church teaching. In doing so, he encourages a false unity which also goes against Traditional Church teaching.
With all the bad popes in pre-VII history of the Catholic Church, you never saw anything like this. And there was good reason for that: it wasn't the teaching of the Catholic Church.
The reason why you and others think this is just fine and dandy is because this has become the norm in the Church these days.