Has anyone been able to speak fluent French from Duolingo?
While I think Duo is a great tool, you have to do more than just Duo to be able to converse.
I'm just starting out in French, so I am basing my comments on my experience in Spanish. I did the whole tree in Spanish (tested out of lots of it), plus took tons of one on one conversation classes (in Spanish speaking countries), plus watched hundreds of hours of telenovelas (Spanish-style soap operas), plus studied grammar online and in workbooks, etc. I eventually became "fluent" in Spanish, but it took all that.
Others may learn faster than me, but I do think you need real, face-to-face communication and be in situations where you are expressing your own thoughts to really learn a language.
I think you need to put yourself in active mode - practice producing language, not just understanding (passive). And duolingo can't help with that directly. Apart from actual conversations with real people perhaps talking to yourself can get you quite close to fluent. If you can't speak yet, try writing, gives you more time. Also translating books (as in whole chunks of continuous text) into language you want to learn is a nice active exercise.
Je pense que c'est très bien pour lire et écrire mais pas pour parler. I learned some French in Grammar school 50+ years ago and have just started this course a week ago. I've dredged up a lot of what I learned plus some but I can see a need to speak it more. It's very good though and I will learn a lot from this course.