Why do people claim that all religions teach essentially the same fundamental truths? It is tempting for those who have not committed themselves to a single worldview to claim this because they have an incomplete, even shallow, perspective of the major claims of various world religions. They also may just want to avoid controversy and see the value of each type of diverse person.
However! Does this claim align with logic, with fundamental religious claims, and can it withstand the claimant's own scrutiny? No. Occasionally. And no. 
Here is how we can highlight the major differences between religions is a way that includes disjunctive logic. Here is also a Christian perspective on the fundamental worldview differences.