You are 100% with what you say about motivation. If you do not feel something is useful or feel really passionate about learning it, it will be nearly impossible to learn.

But I have to disagree when you say duolingo is impractical. I believe duolingo to be the most practical app for learning language out there, which is not to say using apps are the most practical way to learn, but it’s a wonderful tool. We need to make sentences using grammar in order to allow the grammar to process automatically. No sentence is impractical if it has words that you are likely to use and common grammar that’s you are trying to learn, it doesn’t matter how impractical the sentencemignt seem. The only better alternative would be to make a ton of sentences yourself and speak them out with a textbook as a guide

To be fair I have yet to become fluent using duolingo but it is mostly due to the problem you had, I just didn’t see myself using the language any time soon. I really wish I had it when I was studying Japanese now or chinese though!