Average quality is so much higher for certain languages (Clojure and OCaml also come to mind). I don’t mind a 5% pool size when 95% of the alternative can’t build things.

This is almost never a bad thing. It means you have fewer people to compete with when advertising a position and the people that use a niche technology generally have more passion for their craft.

Although it also delays hiring - I work for a startup using Kotlin, and we've had maybe three candidates _ever_ who have used Kotlin beyond hobby projects. And I was one of them!

And I was under the impression that coders were thought of as replaceable cogs in a machine, one just as good as the next.

You might get less volume, but you can use this as an advantage