Farming existed before the combine harvester, and like the combine harvester LLMs are very useful tools in these tasks.
You can't get a useful response from German for Dummies if you ask it to rate the email you're writing in German and let you know what needs improvement, human teachers who can are expensive, and friends may not wish to be constantly bothered by a 40 year old asking the kinds of questions a native speaker might have asked their teacher when they were 13.
Course not. I can make the judgement call "this is good at German" by virtue of all the Germans around me using it.
(Conversely, I'm told it's quite bad at, say, Chinese — though mainly by people online, as there aren't many native Chinese speakers in my life right now).
You can't get a useful response from German for Dummies if you ask it to rate the email you're writing in German and let you know what needs improvement, human teachers who can are expensive, and friends may not wish to be constantly bothered by a 40 year old asking the kinds of questions a native speaker might have asked their teacher when they were 13.