My own experience mirrors yours. My first thought in seeing this was “…why?” Duolingo is a gamified app that feels like learning a language but actually teaches you next to nothing while driving engagement. I get why they got stuck on that path, but why copy it?
They might have found it useful enough to attempt their own spin on it, I guess.
I don't think that Duolino is absolutely useless. But my reason for learning languages might be different from those of others. Some people want to be able to say a few words in the language they are learning. I want to read novels, poetry and philosophical texts.
The approach you take and the kind of vocabulary you want to acquire will differ accordingly.
