Oh but it is. Only tradition says that it isn’t.
The Reformation was quite necessary, in its day. I'm a great fan of the tradition and liturgy of the Church, and I like this Pope, but there will never be any real ecumenism until the Catholic Church agrees that its doctrines are open to question and debate. Every ecumenical effort on the part of the Church always seems end up with, "how can we get you all to come back to us and agree with everything we teach."
The Church never approaches ecumenism on equal footing, prepared to hear out Protestant issues - on theological and doctrinal issues.
But I hold out no real hope, because the Church has backed itself into a corner. It cannot throw out any of its ex-cathedra doctrine, and it cannot change or throw out any of its tradition without losing its mythical infallibility. And therefore complete inventions, like the "assumption" of Mary, can not be revisited, examined, changed, or thrown out. To do so, by the Church, would be a de-facto admission of fallibility.
And though I love so much about the Catholic Church, this Protestant will never agree to any Marian doctrines such as "immaculate conception", "assumption", etc, or that I should pray to the souls of dead human beings who are now alive with the Lord. For most Protestants, anything to do with Marianism is right out, anathema. So unless the Church is willing to agree that Marianism is a private matter and nothing within it is required for a believer who joins the Church, then ecumenism is a wasted effort.
Sola Scriptura meant something, too, and it's too bad so many Catholics and Protestants have forgotten what Luther originally said.
Well, that's not very ecumenical now is it? You heard the Pope so straighten up.