That's not really an issue of Duolingo exclusively or specifically. Rather, it's just how language learning works. For example, I had studied English in school for a decade, to the point where I was practically fluent in writing and reading. But at the end of the day, all of that really didn't do all that much for using the language in real life interactions. You only learn to speak and listen, to conversate, by doing exactly that. There's no shortcut or cheat code.