One of the hardest parts of learning a language is just that building enough vocabulary so you can start stumbling your way through speaking it. Duolingo, Drops and similar are never going to be "the one tool" that you need. But they are a useful way of building some of that initial knowledge to then start reading (childrens books), having horrifically slow bad conversations, and the other things that allow you to learn the language.
Anki is great for learning (and allows the same spaced repetition), and AnkiWeb allows proper synchronization, but you gotta maintain and build your own deck (which itself aids you, but is a lot of work with things like pronunciation) or use another amateur's build deck. The power of Duolingo is that it reuses SVG artwork, and that the TTS engine plus voice sets work reasonably well.
As someone who followed the same method (DuoLingo for vocab, start reading, start talking) and now speaks a second language fluently, I'm not OP but I'll go ahead and vouch for their comment.
Completed the tree, but admittedly it was shorter back then.
I also did it in parallel with the Language Transfer podcast, which I've mentioned on HN before but is an amazing resource for understanding how a new language works structurally and grammatically.
I did find Duolingo valuable, but purely for vocab.
