i would agree that there is an amazing amount of productivity to be gained by reaching for mastery over a language.
that said, the efficacy of that mastery is determined by how "useful" the language is in a wider context. this is, for better or worse, highly influenced by "popularity" when it comes to programming languages.
Mastering something like brainfuck? ymmv ;)
I feel the same way as you do about python about C#/.NET, and I'm happy to have picked C#. I think for most things it would be as good as Python, e.g. web-dev, app-dev. With Xamarin it's a great choice. For data science I'd have to go running to Python or R (maybe I'd do as much in C# as possible), but luckily I don't do much data science.