Language learning courses and tools are just ways to kickstart normal language acquisition, so you don't have to go through the years of gurgling like a baby has to. Learning to communicate in a new language isn't exactly like learning some other kind of skill--it's much, much huger.

When you're speaking your native language, you're decoding and processing complex social signals in real time at multiple levels of structure (phonological, morphological, syntactic, semantic, pragmatic). Even the best AIs can only get a couple of these levels of structure, with significant error rates, and only in a handful of well-studied languages (there are hundreds or thousands of natural languages). How much time does it take for you to learn 1000 vocabulary words? A natural language will have tens of thousands. A comprehensive grammar of the English language would be dozens of heady volumes and have less information about English grammar than any competent native speaker.

Learning a language is just an astonishingly huge task. No course or system can cover it all. Mostly they're just trying to make things easier for you.