In my experience, Duolingo is as good, in fact better than the average class you can get. It won't get you to fluency by itself, but years of bare lessons won't

In my experience, Duolingo is as good, in fact better than the average class you can get. It won't get you to fluency by itself, but years of bare lessons won't either. A few years ago I got randomly interested in Danish, so I started Duolingo Danish. In a few weeks I was able to understand tweets from Danish newspapers. In 4 months I could read novels, slowly but well enough to enjoy them. Do I "know" Danish? Not really, I can't speak past a few sentences and have a hard time understanding it spoken (Danish is a particularly hard one at that). But my RoI for 20 minutes a day for a few months was great. Then my daughter had a hard time with her school English. She knew nothing and could not even follow the glacial pace of her lessons. I bribed her into keeping a 200 day streak in Duolingo and she was suddenly acing her tests. Now she has some interests with English only sources, and that alone is enough to help her keep learning, but duo was a huge kickstarter. My wife also had non existent English from years of classes and needed to at least understand emails at work instead of always passing them by me, and a 300 day Duolingo streak fixed that. I don't doubt that there are very good teachers out there, and you need to complement Duolingo if you really want to learn thoroughly, but it really puts you on track for very little actual effort.