Religion comes from this desire within us, to know and have a relationship with God. Because of sin, this becomes problematic. And instead of coming to know God and worship Him easily, it becomes an effort to even know Him at all. So, more often than not, when humans, trying to know the Lord come up with whatever ideas they have, they get it wrong. And these "religions" that sprout up throughout centuries, throughout cultures, are just wrong. They don't really know Who God is....
...Because of our sin, because of our weakness, we can't know God by our own efforts. And so our God, out of love for us, came into the world and revealed Himself to us. He did this slowly, throughout the Old Testament, with the Israelite peoples. And then He sent His Son, and His Son revealed the Holy Spirit. From this, we now know that God - something we could not have know on our own - is a trinity of persons.
Truly the most profound mystery of our faith: that a single God is three persons....
My job is to follow Jesus Christ the way He set down for me, and to the preach the Gospel that He left us. By that, hopefully, I'll be saved, and I'll be a witness to others who don't know Him, and by His grace they can come to Him.
It's false love to try and water down the faith just to get along with other religions. It's false ecumenism. This idea that we just need to agree to disagree; or let's just get along, let's just find a way to work together...
We must believe that our Church is the only Church of God, the only true religion. All others are false, to varying degrees. Because that's what's taught us.
St Paul so clearly teaches in the Word that the Church is the Body of Christ. Not "is like the Body of Christ" or is "one of" the bodies of Christ. The Church is the Body of Christ. There can be no other.
Our responsibility is to ascent to this in faith, to proclaim it when necessary, to live it ourselves, and not to judge the individuals of other religions.
Ex 34:4b-6, 8-9; Dn 3:52, 53, 53, 55, 56; 2Cor 13:11-13; Jn 3:16-18