Religions do not teach that they are the Only Way, thus causing division. People interpret their religions to mean that.
Each religion was revealed for a certain age in history which is called a religious dispensation, but when people cling to religions of past dispensations and believe they are the Only Way to worship God, it is bound to lead to division and strife. This will never end until people finally realize that religion is all part of one unfolding process of revelation from God to humanity, thus all religions are the Truth from God, each one pertinent to the age in which it was revealed..
Religions are like successive chapters in a book but once we have gone past a chapter we need to move on to the next chapter. Life is like that, we continually grow and evolve, so why wouldn't religion also be like that?
Actually they (most) teach they are the only way, even sects of religion are taught to loath other sects of the same religion.
Is that your god or someone elses god?
Religious books do not change much with time. Life grows, religion is static