Most languages have at least one high quality textbook written for secondary learners of the language. (This is no guarantee that one will be able to read the language that textbook is written in, but English to X is quite common, and some intrepid textbook writers have solved this problem by writing the textbook in the very language it is being taught in, starting with the simplest possible phrases and moving gradually up in difficulty.)
However, language learning is almost entirely a self-guided process. Even if someone chooses to attend a class or hire a tutor for the language, the vast majority of the work has to be performed by the student themselves, with many hours of reading, writing, speaking, and listening. Until recently there has been no adequate feedback loop for these top tier language textbooks outside of asking a speaker already proficient in the language. Textbook authors know this, of course, and for that reason great emphasis has been put on making the flow of examples and problem statements as intuitive as possible for the presumed-alone student.
LLMs change this fundamentally. One can now easily open a language textbook, begin diligently working through the exercises in a linear fashion, and then check their answer with an LLM, and be confident that what comes out will be adequate for the learning process. This makes language textbooks, with their carefully honed examples, much more viable in the competitive meta of language learning materials.
Obviously this is not true for every language on Earth. You’re probably still better off finding a human tutor if only 300 people speak the language you are studying. But most of us aren’t studying critically endangered languages. We’re studying Arabic, or Norwegian, or Spanish, or … English! Chatting with an LLM all day in English is a surefire way to get better English skills, which is probably the most important category of all economically.
Nor does it have to be true that the LLM produces grammatically correct sentences or explanations 100% of the time to be useful - nobody does, not even teachers. I’ve seen LLMs whiff the finer points of Finnish grammar many times in my acquisition process, but in no way does that mean their whole value prop is negated.
Pick up a language textbook today and try it out. You might find yourself surprised by how efficient your progress can be.