I completely disagree. I have been successful in building a new project for my company with myself and the entire team being completely new to Go when we started. Did we have growing pains, and some sub-par decisions? Absolutely. Do we right better Go code today, 4 years later? Absolutely. Did this mean that the project was in any way significantly slowed down by our use of Go compared to the C# or Java we knew before after the first 1-2 months? No, not really. The ways in which Go fit better for our chosen domain completely made up for that (and this all despite my continued belief that Go as a language is inferior to Java and C#).
Now, there are other languages where I'm sure that we would have had significant issues if we tried to adopt them. In particular, switching from the GC languages we were used to to a native memory language like C++ or Rust or C would have surely been a much bigger problem. The same would have probably been true if we had switched to a dynamic language.
But generally, deep language proficiency has less value in my experience than general programming proficiency, and much less than relevant domain knowledge. I would hire a complete Go novice that had programmed in Python in our specific domain over someone who has worked in Go for a decade but has only passing domain knowledge any day.
Now, there are other languages where I'm sure that we would have had significant issues if we tried to adopt them. In particular, switching from the GC languages we were used to to a native memory language like C++ or Rust or C would have surely been a much bigger problem. The same would have probably been true if we had switched to a dynamic language.
But generally, deep language proficiency has less value in my experience than general programming proficiency, and much less than relevant domain knowledge. I would hire a complete Go novice that had programmed in Python in our specific domain over someone who has worked in Go for a decade but has only passing domain knowledge any day.