Yes, the type is very interesting to know. That's why other languages make it known. Ignoring the entire discussion to reply twice with "nu uh!" is not very productive.
When the return type actually matters, auto should be avoided unless there's no way around it. But that's why we have "Returns:" in Ddoc. The function signature itself is not the complete documentation. I mean, you're acting like all D functions are documented to return auto. They aren't. It's used where it needs to be.