It's the same as Tinder. The business isn't about getting you dates, the business is selling you the fantasy of getting a date. Those two things are different, but for a new user, difficult to distinguish. Duolingo offers you the fantasy of speaking a new language.

Of course it is possible to learn a language using Duolingo, just like it is possible to get dates on Tinder, but it's just not a good method. If you're new to learning foreign languages, you'd be better off signing up for a course (but that costs time and money), and if this is your n-th foreign language, then you'd rather get a book and some boring flashcard app.

Part of the problem might be that no one wants to pay anymore. I'm happy to pay for a course, but there is not a single in-person language course in my city left for the language I wanted to study.

I booked the the single remaining one last year and shortly before the start they announced they will not run it anymore and instead do online classes only. Apparently the rent is too high and it just isn't viable anymore.

It sucks all around :/

You're learning words and random phrases like "My uncle takes his plants for a walk every week".

Not stuff that's actually useful.

But it still builds vocabulary and is better than nothing for the price.

Knowing what a sentence in the target language ought to feel like is very useful, though. You're learning what order the words go in, how to match genders, how to express different tenses, where to put prepositions, and so forth; the point is not to memorize the specific sentences but to absorb the structure of the grammar.

When learning languages the things you should learn first are food, health and shelter.

Just by knowing a few key phrases in the main categories and the probable answers to those in a language will help you get by a lot better than "I like to ride my bicycle in the rain on the weekends" :D

Functional fluency over grammatical competence.

Thanks - that's not a perspective which had ever occurred to me. I just assumed that learning a new language would require a long period of steady practice, and that's what Duolingo seems to be built for; but if people are often approaching it looking for something more like a glorified tourist phrasebook, I can see why they might complain about the abstract nature of the practice sentences.

A lot of the time, you aren't even learning how to translate the sentence. It's more like you've recognised basic sentence structure (in your own language) and managed to make a sentence from:

plants for week walk My every uncle takes a his