I can understand why so many people desire this to be true. There is a prevailing idea that much of the conflict, violence, and war in the world is caused by differing religious belief. Therefore, the reasoning goes, if we can eliminate the differences in religious belief, then we can reduce the conflict and suffering in the world.
First, the assertion that religion is the cause of war and conflict is not supported by the evidence. You can read more about a survey of wars and their causes through history here. You can also read a more philosophical review of a book on the subject here.
Beyond that, however, is this question: Aren't all religions basically teaching the same thing? The short answer is: no.
If religions were circles, there would certainly be some overlap of the venn diagrams. Nevertheless, each religion has certain core teachings that cannot be reconciled with those of other religions. In fact, many of these central beliefs are actively in opposition to the ideas of other religions. For Christianity, the central and non-negotiable issue is what Christians call "the person and work" of Jesus of Nazareth.
Christians trust our lives to this truth: Jesus is God in human flesh, come to rescue and renew a broken and dying world. He did this by dying on the cross and rising bodily from the dead.
The Campaign for Core Christianity has a very good article about how Christians view comparative religions, titled: "Do all Religions Just Teach Love?"
Here is a quote:
When a person concludes that all religions are basically the same, they’re defining the various religions of the world on their own terms instead of letting the terms define themselves. If religion is primarily about being a good person, then sure, many of the religions out there can assist someone in modifying their behavior, but religions like Christianity aren’t essentially about being “good people.” The Christian religion is all about the God who lovingly pursued people who weren’t very good at all, in fact. That’s why the message of Christ’s death and resurrection is one of the vital organs of Christianity.
You can read the whole article here.