I... disagree. The joy I get from learning a programming language does not come from knowing that it is useful. Rather, it comes from engaging with its abstractions and figuring out the associated mental puzzles.
On a related note, I recently realized that I am barely writing code these days (instead I am reviewing a lot of LLM-written code and nudging it in the right direction) which will make doing the advent of code (which I usually use to play with a language I have never used) without any LLM help even more enjoyable: it will be both the fun of figuring out those puzzles in a new language, and stretching my code-writing muscles.