Fifty years ago, most denominations had some degree of closed communion — people were generally nice about it, but the denomination was the gatekeeper.
Since the 1950’s this rather Brethren way of doing Church has largely broken down in the West.
People who are not personally excommunicated are admitted on the basis of baptism, and the whole Church, not the denomination is the medium of the Sacrament.
The institutional denomination is only trustee for the Lord, to whom the Sacrament belongs.

In the good old days saying the Lord’s prayer with other Christians was a mortal sin for Roman Catholics, but that was many years ago. Conciliar theology has a structure to support Eucharistic hospitality, which is only offered in certain closely defined circunstances.
In Hanover in 2005, my eyebrows raised as the (now retired) Cardinal Archbishop of Mainz described the current restructions in his denomination as a “
thorn in the flesh.”

In Bremen I stayed with a delightful Catholic host, who told me the hot ticket for Saturday morning’s Bible Study was
Fullbert Steffensky, Professor Emeritus at Hamburg.
He was now a Lutheran, having started out as a monk of
Maria Laach — the place Adenauer found sanctuary from the Nazis in 1934 (though that’s not quite the whole story of the monstery at that time).

The Bible Study considered
Genesis 16 and Hagar the slave woman. She is not entirely outside God’s blessing, and we were led into considering the
probem of religious absolutism and the inability of some Christians and others to believe God has blessed anyone but their in-group. He leapt straight from there to an incident at the Berlin Kirchentag in 2003, where large crowds had been banned from intercommunion. What right had ecclesiastical authorities to try and deprive the people of God of hope?
As I mentally fell off the seat, given the style distance between the presentation and our customary stately Englsh ecumenical quadrille, the preacher continued. 
The basis of Communion is the mercy, gift and call of God, not what he scathingly called “
die Einheitlichkeit in einigen Sätzendes Bekentnisses. (loosely, “the oneness of a sit-down of acquaintances”) It was pointless for ecclesiastical authorities to say the Church wasn't ready for such a thing, if all they meant was that they weren’t.
Now, Ecumenical diplomats, sit down somewhere comfortable and pour a stiff drink, as I quote the published text:
Wir können nicht darauf warten, bis die letzten fußkranken Mitglieder von Kirchenleitungen angekommen sind und das Mahl für erlaubt. (very loosely, “We can’t wait for the last lame duck Church leaders to catch up and join us at the table...”)

Dr Steffensky very much hoped that at future Kirchentage people would just go ahead and eat as the Lord commanded, concluding
Auf Dauer werden die Bischöfe schon fördern, was sie nicht verhindern können. ( loosely, “The Bishops will soon enough require what they can’t prevent.”)
Boooom! Right, my English Ecumenical Chums.
This is certainly Provocative stuff that you wouldn't hear in a gathering of 125,000 Christians in England.
Is it “Liturgical Terrorism” or the Future?