I agree with your last point. I get the criticism of Duolingo and it is fair, but I can't agree that it is completely useless. I learned/am learning French. I can get by with non-English speakers and people won't immediately switch to English when they hear me.
It took about 5 years of on and off practice. Not sure how much actual time I put in. Duolingo was one aspect, where honestly I probably learned like 75% of my vocabulary. I also have a French wife and friends, took classes, hired teachers, watched movies, read news, etc, etc, etc. I probably could have got to where I am without Duolingo but I'll never know. Learning a language is a pain in the ass and I don't think any one thing is really going to do it. Duolingo is free and can be one aspect out of many that will help get you there.
It took about 5 years of on and off practice. Not sure how much actual time I put in. Duolingo was one aspect, where honestly I probably learned like 75% of my vocabulary. I also have a French wife and friends, took classes, hired teachers, watched movies, read news, etc, etc, etc. I probably could have got to where I am without Duolingo but I'll never know. Learning a language is a pain in the ass and I don't think any one thing is really going to do it. Duolingo is free and can be one aspect out of many that will help get you there.