Well, for existing applications it is extremely difficult, not because Elixir lacks many important features that C# delivers (although I'm sure it does lack some, and vice versa in a big way), but more just because rebuilding any project that's had hundreds or thousands of person-hours poured into it, that's currently satisfying hundreds or thousands of business requirements which may or may not be documented, is a huge project with few rewards; the investment is huge and the return on investment is... I mean, being on {sexy new language} is nice, but nobody's paying you for that.
But that's not what the OP's job is talking about. They just got a different job using Elixir, and are learning the technologies the same way anyone else does, and they're excited about this instance of it enough to write about it.