500 days of Duolingo: What you can and can’t learn from a language app
Learning a language requires immersion.  That's why classes with other students are more effective than flashcards.VR has potential to really make a difference here.  Imagine you load a VR level.  It's a busy outdoor market in Taipei.  In your inventory you have some cash.  NPCs with AI and chat logic are around you interacting.  Your goal is to buy some bread and get to the subway.  You see a vendor with some bread, but don't remember the word for bread.  You hear a NPC talking to the vendor and buying some bread.  Now you remember.  You speak the words, but the vendor doesn't understand.  Your tones are off.  You try again, this time the vendor smiles and says how much it costs.  You give cash, take the bread, and walk to the subway.  The next level, buying a subway pass...This basically already exists in RPG games.  It just needs mic support so you can speak and good "game" design that's designed to help learn the language.  Playing this for an hour a day would be more effective than an hour of flashcards.  And also a lot fun.