Well, I do understand that since Vatican II there has been a much more visible ecumenical outreach by the RC Church, than prior thereto.
This outreach is not unprecedented, however.
The Council of Florence was a meeting with the separated Eastern Orthodox churches. Pope Eugene IV not only invited them, but shared a prayer with them.
and
the Council of Trent invited Protestants to attend and participate, assuring them safe passage and leave at any time they wished, etc.
And several Popes have held discussions with, and at times been moved to assist or aid, Jewish people, going back even further in time than the above.
Now then, yes...we have indeed seen a widening of these types of activities since Vatican II. But the idea that the RC Church should shut itself up and not share anything with anybody else on planet earth is ludicrous and does not hold up too well when we examine the real history.
The easiest ecumenicism or sharing, albeit still not without challenges, is with Orthodox, Protestant, and Jewish believers... the Biblical faith traditions, which all pray to the same God (however understood, nobody contradicts the basic fact that it is all the same God of Abraham, Isaac, and Jacob), and which share essentially the same moral code or teachings.
Even these outreach efforts are difficult for all concerned.
This is why I do not feel very comfortable with ecumenical outreach to non-Biblical traditions, groups which do not pray to the same One True (Biblical) God.
And I am especially worried about any outreaches to Islam, which explicitly rejects Christianity in its scriptures and which seeks to subjugate, or kill, Christians.
But yes the recent Popes have made such attempts.
Don't you see? What "history" are you referring to? The Catholic Church has already shut itself up since VCII. The Church no longer proclaims, Christ, the Sovereign King, to all nations; nor does it preach, "extra Ecclesiam nulla salus".