I've only recently started the classroom learning, week 5 just began, and I'm in there five days a week, four hours a day, so that's really great and the outcome required is, I think, B1 level. Duolingo over 18 months contained so little vocabulary and grammar, plus I stopped it maybe 18 months ago too, so its impact was restricted to about one day's worth of class.

I did five years of French at school and three years of Spanish and definitely enjoyed the Spanish more.

Duolingo is basically the app equivalent of flashcards. It's a little smarter than that, but not much. If you're serious about learning a language, it absolutely has a place. But Duolingo __alone__ is not going to make you competent, much less fluent.

Personally, I'm happy with it. I took years of Spanish and started with Duolingo in French with zero prior French, and I can now recognize phrases and hold some basic conversation; for 5 minutes a day with no significant continuous time commitment that's not bad!