People always under-estimate the cost of properly learning a language. At any given time I tend to have a "main go-to language". I typically spend 2-4 years getting to the point where I can say I "know" a language. Then I try to stick to it long enough for the investment to pay off. Usually 8-10 years.
A surprising number of people think this is a very long time. It isn't. This is typically the time it takes to understand enough of the language, the compiler, the runtime, the standard library, and idiomatic ways to do things. It is the time it takes to where you can start to meaningfully contribute to evolving how the language is used and meaningfully coach architects, programmers and system designers. It is also what you need to absorb novices into the organization and train them fast.
A surprising number of people think this is a very long time. It isn't. This is typically the time it takes to understand enough of the language, the compiler, the runtime, the standard library, and idiomatic ways to do things. It is the time it takes to where you can start to meaningfully contribute to evolving how the language is used and meaningfully coach architects, programmers and system designers. It is also what you need to absorb novices into the organization and train them fast.