Sure, knowing your way around the ecosystem is a thing. But that ecosystem has to exist and be kept up to date. And you wouldn't want to hire someone who was to

Sure, knowing your way around the ecosystem is a thing. But that ecosystem has to exist and be kept up to date. And you wouldn't want to hire someone who was too keen on reinventing the wheel anyway... Plus, it is a slam dunk case that most organisations will not benefit from choosing a "best" language for every project or use case and should instead settle on as few as possible... One HLL (e.g. Python or Tcl or Perl) and one low-level (C or C++) is probably the best bet for 99% of organisations.