[jrochkind1]

I think domain knowledge has been under-estimated in general. Which I think applies to tools too, such as programming languages. Knowing the affordances, the options, the libraries available, etc -- matters.

Developers aren't interchangeable widgets.

Sure, a really good engineer will be able to learn a new language. I don't actually disagree that it can make sense to hire developers who aren't yet expert in the language they are using, sometimes it does.

But a really good engineer learning a brand new language to them will still take a year or two until they approach the productivity and quality of decision-making of a really good engineer who was already well-experienced with the language. Will a really good engineer learning a brand new language be more productive than an inexperienced or poor engineer who has messed with the language for a year? Sure, ok.

General programming aptitude matters a lot; but experience with the tools they will be using matters too, it isn't irrelevant.

[c7DJTLrn]

>learning a brand new language to them will still take a year or two until they approach the productivity and quality of decision-making

I don't agree unless we're talking about something like Rust or C++. Python, Java, and JavaScript are all very easy to pick up once you understand the concepts they share. I would expect any developer to at least know the basic syntax of Python for instance even if they don't write it daily.

To me, if somebody only knows one language but they're an expert in it, it indicates a lack of ambition, curiosity, and willingness to face new challenges which are desirable traits to look for when hiring. And unfortunately for such people there's polyglot experts out there that can be hired for the same price.