> I wonder, at which point it is worth it to make a language?

AT ANY POINT.

No exist, nothing, that could yield more improvements that a new language. Is the ONLY way to make a paradigm(shift) stick. Is the ONLY way to turn "discipline" into "normal work".

Example:

"Everyone knows that is hard to mutate things":

* Option 1: DISCIPLINE

* Option 2: you have "let" and you have "var" (or equivalent) and remove MILLIONS of times where somebody somewhere must think "this var mutates or not?".

"Manually manage memory is hard"

* Option 1: DISCIPLINE

* Option 2: Not need, for TRILLONS of objects across ALL the codebases with any form of automatic memory management, across ALL the developers and ALL their apps to very close to 100% to never worry about it

* Option 3: And now I can be sure about do this with more safety and across threads and such

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Make actual progress with a language is hard, because there is a fractal of competing things that in sore need of improvement, and a big subset of users are anti-progress and prefer to suffer decades of C (example) than some gradual progress with something like pascal (where a "string" exist).

Plus, a language need to coordinate syntax (important) with std library (important) with how frameworks will end (important) with compile-time AND runtime outcomes (important) with tooling (important).

And miss dearly any of this and you blew it.

But, there is not other kind of project (apart from a OS, FileSystem, DBs) where the potential positive impact will extend to the future as much.