Is there really a difference? I feel like if you don’t know something, that kind of makes you stupid, right? If you don’t know historical facts or mathematics—at least the harder stuff, like algebra or calculus—or if you don’t know about advanced political topics, then you’re kind of a stupid person, not just ‘ignorant.’
Not always. Someone close to me has issues with executive dysfunction and short term memory as a result of brain trauma. She really struggles with algebra and she’ll almost certainly never learn calculus even if she wanted to.
That’s a different issue entirely. If they think they’re experts at judging what’s useful, that may be the Dunning-Kruger effect.
I think we overuse dunning kruger. “useful” is very contextual. I would agree that for many people it would take some specific and dare I say unusual circumstances where learning another language is particularly useful to them. There’s some use in that you get a bit of a puzzle to overcome, you can potentially eventually get good enough to consume content in this other language (though one thing LLMs are pretty good at is translation), maybe you get a more direct exposure to Dovstoyestky (sp?). Cool and all, but probably not going to get them a better job or help them with most life tasks.