My wife only did 50 hours of duolingo in total the past 2 years. Combine that with me teasing her in Dutch and she’s actually making progress.
Duolingo is a chill tool to learn some vocab. That vocab then gets acquired by talking to me. We talk 2 minutes Dutch per day at most. So about 11 hours in total per year.
She is 67% done with duolingo. So we bought the first real book to learn Dutch (De Opmaat).
That book is IMO not for pure beginners. But for the level my wife was at, it seems perfect.
Human speech is around 150-200 words per minute; even going slow, 2 minutes a day of real talk is probably more vocab than 10 minutes of Duo. And with better feedback, a human rather than a cartoon casino.
I finished the whole tree in French and had nothing to show for it either. It really is a fun way to feel like you're learning, without connecting you to the language or culture in any significant way.
For me - nothing beats in-person classes in lieu of a native speaker whom you can interact with. Being forced to actually speak the language in “mock settings” makes all the difference.
And even if you don’t get your grammar completely right, you will learn enough to survive in a real-life setting.
I learned Spanish through a combination of both - I took Spanish classes after I started dating my Mexican wife, enough to get conversational. Then I started interacting in Spanish with her family, which helps me now maintain the language without needing the classes.
I feel this whilst learning (trying to) German: when I think "how I would say this in German?" I got nothing less than a blank on my mind. But I'm a good "speaker" though, and sadly, I feel I'm not going anywhere as well...
Watch Dark on Netflix in original German on repeat, great way to subconsciously make note of tones and pronunciation while also watching an awesome show. Be very intentional about it though.
Surround yourself in the language. In Germany we have almost everything dubbed, so you can watch pretty much any popular movie or TV series in German or read any popular book in German. Besides that there are also quite a lot of German productions.
Wow I forgot about that! When I was using it for French many years ago, I imagined they were using it as a way to get generate free translations, but still found it enjoyable and useful.