I used to arrogantly think I could be productive in any language given a week or so to adapt. I often used the phrase "a good dev is a good dev in any language." That belief was rather abruptly broken when I joined a project using C++/CX it was so far outside of my previous experience that I had a really bad time of it. I happily picked up the actual language very quickly. It was the surrounding ecosystem of compiler…
I worked for a company a few years back doing ASP.NET (my experience is mostly Linux based tech, but you can pick up a language, right?). The language was fine, the design patterns used all quite standard, but the project had an array of frameworks and libraries which made maintaining it painstaking.
In fact, I think you worked on it too.