I sense a goalpost moving here. The point of the blog post to which I answered to was: I have to redo all my programs to follow the "idiomatic" way.
Now we are at "other programmers could use new features, so I still have to learn them". And yes, that is true. And that will always be true as long as a language has new releases. Even if all those releases were library changes and not syntax changes/additions. The only way to stop this would be to stop all language development.
Even worse would be if someone pulled in a library... That requires much more cognitive load and doc-reading than something like try! -> ?
Or the worst of all possible worlds -- pulling in a macro-based framework
I think ruby (which in general I still love) has become a major offender of this. "If you don't like it don't use it" is not a good answer for exactly the reasons you explain.