I think that is unnecessarily hostile; I believe Lean 4 can become a very capable programming language for mundane tasks!

Hostile? I just stated that the audience isn't programmers.

The age of guilds has long passed

Are people like these not programmers? https://leandojo.org/

How can the audience of a general-purpose programming language not be "programmers"?

I don’t think that your post is hostile. But from what I’ve heard, it is untrue because Lean 4 is intended to be a general purpose programming language, not only a theorem prover. I can’t find a source that directly states this goal but at the least this paper by Leo de Moura and Sebastian Ullrich presents it as a programming language:

https://link.springer.com/chapter/10.1007/978-3-030-79876-5_...

Microsoft also sponsored David Thrane Christiansen’s book, Functional Programming in Lean[1] (which I’m sure you know about!). That is another indication that they intend to reach programmers.

[1] https://leanprover.github.io/functional_programming_in_lean/

It seems general programming is more in focus now, but for context, the "Programming in Lean" book was only completed recently as compared to the multiple theorem proving documents which have been around for a while. The Christiansen book looks worth waiting for though and I really hope Lean can gain popularity as a general purpose language.