Aren't all religions different paths up the same mountain?
No. They contradict each other on the biggest questions: is there a Creator, is there a self, what happens at death, who is Jesus. Even the Buddha did not think all teachings were equal.
The famous parable of the blind men and the elephant actually comes from a Buddhist text, the Udana. But notice how it is told: the Buddha compares teachers of other religions to blind men who each grasp one part, while he, like the king, sees the whole elephant. The parable is a claim to see the truth, not a claim that every view is equally true.
Christianity makes the same kind of claim, with a public reason: Jesus said he is the truth, and God raised him from the dead. Different paths cannot all be right when they say opposite things.
In the same way, mendicants, the wanderers of other religions are blind and sightless. They don’t understand what is beneficial or what is not beneficial, nor what is the truth and what is not the truth. That’s why they are fighting, quarreling, and disputing, continually wounding each other with barbed words.
Udana 6.4:31.1-31.3, Followers of Various Other Religions (1st) (tr. Bhikkhu Sujato) · context
6Jesus said to him, “I am the way, the truth, and the life. No one comes to the Father, except through me.
John 14:6 (WEB) · context
30The times of ignorance therefore God overlooked. But now he commands that all people everywhere should repent, 31because he has appointed a day in which he will judge the world in righteousness by the man whom he has ordained; of which he has given assurance to all men, in that he has raised him from the dead.”
Acts 17:30-31 (WEB) · context
Reason 10: The Buddha died and his relics were divided. Jesus' tomb is empty.