> Languages and ecosystems that are more mature and take stability very seriously, like Go or Clojure, don't have the problem of "LLM hallucinates APIs" nearly as much.

Counterexample: the Wolfram programming language (by many people rather known from the Mathematica computer algebra system).

It is incredibly mature and takes stability very seriously, but in my experience LLMs tend to hallucinate a lot when you ask them to write Wolfram or Mathematica code.

I see the reason in two points:

1. There exists less Wolfram/Mathematica code online than for many other popular programming languages.

2. Code in Wolfram is often very concise; thus it is less forgiving with respect to "somewhat correct" code (which is in my opinion mostly a good thing), thus LLM often tend to struggle writing Wolfram/Mathematica code.