Is ecumenism an important part of religion?

Yes if it is applicable to current paradigm. If not, it's as useless as the road map of 2,000 yrs ago. The Ecumenical Movement can be dangerous spiritually to the church, because The Bible says that in the last days the whole world will be "as one," united under the Antichrist, including all religions. So the Ecumenical Movement is just paving the way for a one-world religion of Antichrist.