The best aspect was that you can learn any time you have 5-10 min spare. At the bus stop, a coffee break etc.
But it can only get you so far.
After finishing Duolingo French course I took to Memrise to build the vocabulary: 500 verbs, 500 adjectives etc.
In parallel, I'd read local newspapers online, and Google Translate any word I didn't understand.
This gave me a reading comprehension but talking was still difficult.
I only learnt talking proficiency by joining a French company where everyone would talk French at lunch breaks. (First one was more international with many non-speaker fresh grads, talking English).
After that, watching a lot of TV with subtitles to improve listening.