That seems most likely to me. After all, religion is that to which one binds oneself, from the Latin religare. It's very hard to say that you accept the beliefs of others where they contradict those things that you believe.
I consider for how long the mainstream Christian denominations have been working towards ecumenism, and how little real progress has been made. Sure, there's a World Council of Churches, but the Catholic Church participates only as an observer, not a full member. It was in 1920, more than 100 years ago, that the Ecumenical Patriarch of the Eastern Orthodox Church, Germanus V of Constantinople, wrote a letter "addressed 'To all the Churches of Christ, wherever they may be', urging closer co-operation among separated Christians, and suggesting a 'League of Churches', parallel to the newly founded League of Nations". And tghis is as far as they've got, in all that time?
Well, hold your horses, I would say there has been a lot of good progress, for example:
- The Anglicans and Catholics, where I am, have a very close relationship and work with each other exceptionally well. The priests all know each other and invite each other to participate.
- The laity are emphasising understanding and acceptance. The local Anglican Cathedral has icons in and is very hospitable to all denominations.
- The books that are being produced by formerly partisan groups are much, much more ecumenical; SPCK, for instance, started as an Anglican Mission but now caters to every denomination, including and perhaps especially Roman Catholics. In line with this, there are more ecumenical Bibles being produced and read.
- Things like the Anglican Ordinariate are becoming common.
- The Anglican Church is very accepting of things that, just a few decades ago, would have been sniffed at, such as praying the Rosary.
- The Catholic, Anglican and Scottish Churches recently went together to their communions in Africa to oppose the proposed legislation to ban homosexuality.
- The Roman Catholic Church has allowed the Eastern Catholic Church to start using its own forms again, including dropping the Filioque and other such practices. This is catching on in the West, too.
- The Archbishop of Canterbury recently said 'Anglicans recognise the Pope as the father of the Church in the West'.
The Eastern Orthodox Churches, I am afraid to say, have been an outlier here, and cannot even call a council of themselves, let alone have ecumenical dialogue with others. The two groups doing the best at this are the Roman Catholics and Anglicans, with the most dialogues; second are the Lutherans, iirc.