Of the 8 or so apps I tried, Duolingo was by far the worst. It doesn't feel like it teaches me the language whatsoever, but is instead very good at teaching me the gamification.

I find that Duolingo is the least useful of these apps. Its main advantage is that it's easy and a small commitment if you decide to do one or two lessons every day. For the rest I don't understand why it's so popular. Duolingo's main strength is that it makes you actually construct the language instead of just memorizing individual words or expressions but I'm not super impressed with that either, mainly because in my experience it's very, very common to have a sentence rejected because it didn't match the internal "regexp" used to validate it even though it's perfectly correct (and sometimes these mistakes linger for literally years despite being reported). I actually got a very mediocre result in the placement test for the "French for English speaker" tree despite being a native French speaker who's reasonably fluent in English, mainly because some perfectly correct answers were rejected by the system. That really destroys your confidence when that happens (both in yourself and in the app).

You have a forum to discuss these issue which contains some very valuable information but it's the worst forum software I've ever used bar none, it feels like a teenager's first PHP project in the early 2000's.

Oh and if you use the mobile app it'll have you build the language by selecting one full word at a time, which means that you usually won't have to thing about the conjugations/declensions and just vaguely remember what word means what. It's fine for English, not so much for Russian and its complex declensions and aspect system.

For vocabulary Anki and Memrise easily win because they only do that and they do it well. You can find podcasts aimed at learners of many languages to improve oral comprehension and LingQ is great to improve reading comprehension, although it's expensive for what it is and I feel like you could make a better clone of it in one weekend.

In general I haven't been really impressed by any of these language learning apps, it seems that they really lack the resources to do anything but the bare minimum. It's probably too niche to generate some real R&D.

So overall if you enjoy Duolingo then stick with it, but keep in mind that you probably won't get anywhere just using this app. If I had to recommend only one language learning app it would be Memrise because it's got some decent decks for many languages (including user-contributed ones) although of course you can't learn a language solely by memorizing the dictionary.

The streak is actually the only thing I really like about it, I want to keep it going because it shows me how long I've been working on it. For everything else I completely agree with you, Duolingo is borderline worthless for actually learning a language IMO. I can make a random list of complaints in no particular order:

- The spaced repetition aspect is ridiculously poorly calibrated, at least for me. Basic words decay way too fast which means that if I actually try to keep the skills "golden" (in the pre-crown era) I keep drilling the same basic skills again and again. Anki or Memrize manage that tremedously better. It's not even that complicated to implement correctly, I wonder why it's so crap. Maybe to keep you coming back and stretch the existing content? Now with the crown system they got rid of skill decay altogether, instead having you drill the same sentences an ungodly amount of time to reach a higher skill level. Also no matter how much I've drilled any lesson the majority of the exercises are asking you to translate foreign-to-native instead of the other way around, which would be more interesting as you improve.

- The actual "lessons" for each skills are so bare bones that they're basically useless. I think they know that since I don't think they're accessible at all in the android app. I know that grammar isn't sexy for most but if you want to learn a language you'll have to bite the bullet at some point, an english speaker will have some trouble learning the nuances of the perfect and imperfect past in romance languages by examples alone.

- Meanwhile, on top of not actually teaching you proper grammar they like to mix concepts in the same lessons, because otherwise it wouldn't be confusing enough. For instance the Portuguese subjunctive course contains examples that are actually imperative but "by chance" happen to have the same form as the subjunctive. Because obviously the subjunctive is so trivial that you have to spice things up by adding a completely different tense in there.

- The actual vocabulary they teach you is absurd. You can do the entire tree and not know how to say basic stuff, but you'll be able to say "the painter opens the power outlet" or "my tiger ate my pillow". Those are real examples.

- Worse than weird vocabulary you also have very confusing sentences. For instance take a look at this: https://www.duolingo.com/comment/2121481$from_email=comment&... "Se nós nos encontrássemos mais vezes?" which is translated by "If we met more often?". What does that even mean? It's not even a full sentence. And that's for the past subjunctive lesson, you know, that trivial thing that definitely requires trash sentences like those. And it's been there for 4 years judging by the comments, so the authors of the course stand by it.

- These types of weird sentences are super common and they keep you wondering if you're not getting an idiom of the language or if it's just a super weird sentence. 90% of the time it's the latter.

I don't understand why Duolingo is so popular, IMO Memrise is massively better. It's a lot more focused, it only pretends to teach you words and simple phrases, but at least it does the job. If you want to learn a language buy a good grammar book, a dictionary and drill vocab on Anki or Memrise. Use something like lang-8 to practice your writing. Forget Duolingo.

I do enjoy their "Duolingo Stories" service though, but there's not enough content there to keep you busy for very long and there's no "replay" value.

This definitely rings true. I was using it in the hopes it would help me provide some structure to teaching my kid portuguese (and it does to some extent), but by the time the app says a lesson is "complete", my kid is still a long ways away from having memorized it (and he's 5). I tend to complement it with a boogie board and repetition over the course of several days to really nail down new vocab.

I also wish it had some feature to introduce foreign concepts (e.g. gendered articles in portuguese). It's very awkward to try to explain the difference between `the`, english `a`, and portuguese `a` (and the remaining counterparts `o`, `um`, `uma`) for example, and the word matching exercises can get quite confusing.

Then again, teaching is not really their goal; rather, they'd sell you a language learning game.

I learned German at a University in a German speaking country, and the classes were completely in German from day one which I found helpful. I also bought quite a number of books and studied quite a lot before I become fluent.

So I don’t think an app is a one stop solution, it takes a lot of material, I’m not sure why people think any one system is enough, especially considering you never stop learning a language. Fluent just means you know enough to continue to learn in the language on your own.

I (tried to) use it to learn Asian languages, for what it's worth.

I’ve learned more Greek in 2 years now with that combo as an adult than I did in a decade learning Spanish as a child by only taking classes. The only thing more effective was living in a city that only spoke the language I was learning after I had achieved a certain level of proficiency.

Duolingo made me feel like I was learning a language and having fun while doing it, but every time I looked back on using it, I observed I really wasn’t learning very effectively with it. It’s far too robotic and impractical in my experience.

[0] https://www.languagetransfer.org/

I see Duolingo as more of an interactive digital textbook, but as always there is a gap between completing exercises and applying your knowledge to the real world.

Over the last couple of years, I've invested some serious time into learning Portuguese, first in Duolingo and then in an actual classroom. Duolingo was definitely helpful for reading proficiency, but did almost nothing for my conversation skills (let alone pronunciation). The real classes helped with the conversation skills, though I ended up supplementing them with a spaced repetition app for vocabulary drilling. Grammar is still lacking.

Another Duolingo language that I've spent quite a bit of time on is Yiddish, and I find that I can now read it quite well — but only in the exact font the app is using. I'm not entertaining much hope of ever being able to write or speak it.