Exactly my problem with Duolingo. It is great for Vocabulary, but in the end it's just knowing it by heart, and I was suprised there are no real courses explaining you the synthax of a phrase or some other advanced rules.
I don't find it great for vocab either, Anki or Memrise are massively better IMO since they only do that and they do it well. Of course it Duolingo you get the words in some context which could be better but since half the time the context makes no sense anyway why bother? I just did a Duolingo review about "household items" right now and it repeated twice the word "stairs" and thrice the word "kitchen", words I have no real trouble with. How about giving me some vocabulary I actually need to practice instead?
And at least on Anki or Memrise you can select decks that match what you want to learn, such as getting the basics to order at a restaurant or ask for directions. On Duolingo I think I've learned how to say "the bishop sends a pineapple to the queen" before I learned how to say "bathroom".
