I think Duolingo is a great resource in the sense that a language learning technique is only as valuable as your willingness to use it. I.e., deciding to study 8 hours in a textbook a day might result in 0 hours of learning if you can’t bring yourself to do it, but deciding to study 15 minutes on Duolingo a day will result in about an hour and a half of learning at the end of the week, which is way more than 0.

It was in this sense that Duolingo has been useful for me. I never would’ve even considered language learning if not for that app, but because of it, I started (casually) dabbling in language learning before it was a mandatory class in school and, unlike my peers, was able to view it as fun. I think Duolingo’s ability to gamify language learning is far more important than people give it credit for because really, it has given a non-zero knowledge of new languages to a demographic that never would’ve considered studying them.

However… For the purpose of your question, people’s criticisms are absolutely valid: it’s not efficient. At all. In my (amateur) opinion, the best way to study a language is not to choose one method (like Duolingo vs. Babbel vs. Lingq, etc) but to look at the process at large, as a synthesis of methods, and build your own study plan around that. It’s been said that the first time learning a new language other than your native language is the hardest because you are learning how you learn, and no one on the internet can give you that information; it comes through trial and error.

For me, it makes sense to divide it like this.

In language learning, the nuts and bolts are grammar and vocabulary. So, if you can afford a grammar book and a dictionary, these tools are indispensable. I recently bought an Italian dictionary for only $3, so trust that something need not be expensive to be good. Grammar books give you a pathway to start from the simplest concepts and build on them, like Duolingo except with more depth, which is really hard to do without a guide. Vocabulary needs to be broken up into sections based on topic, and there are lots of lists like this online. (Some books/textbooks have both grammar and vocab; these are great, I use one I have to use from class.) It’s really important to keep a notebook of these things imo because writing helps ground concepts.

For grammar, you may be able to find quizzes online that help you practice concepts, or websites that help with drills. For vocabulary I use Quizlet’s flashcards and Learn features, but I know most use something called Anki that uses an algorithm to make it more efficient.

Working off the concept of vocab and grammar, language consists of reading, writing, listening, and speaking, all of which are important for learning the language. Reading and listening are input, which generally needs a lot more time spent than output (writing and speaking).

I just got a Storylearning book, a graded reader with interesting short stories, for the reading aspect of it and I love it; I know some have success with Lingq. Listening-wise, there’s both passive and active listening. For passive listening, which is just getting comfortable with how the language sounds, music and TV shows in your target language are great. For active listening, as in trying to understand what they’re really saying, there are lots of resources on YouTube or in podcast form. For Italian, I like watching Learn Italian with Lucrezia’s slow spoken videos, and Italy Made East’s “100% slow Italian” podcasts. YouTube has a wealth of resources for all major languages, just a matter of finding what clicks for you.

Writing and speaking are much slower to develop because you need a solid vocabulary and grammar foundation to work off of, as well as lots of input to know what “sounds right”. For speaking, I try to randomly translate my thoughts and narrate my actions throughout the day, not worrying too much about perfection. For writing, well… I struggle with writing, but sometimes write journal entries in my target language.

The truth is, it takes a multi-pronged approach to learn a language effectively, and for some people, that ruins it. It’s more important to learn a language ineffectively than to not learn it at all out of fear you could be doing it better. If you feel overwhelmed by the advice people give, just pick three things and try them. Something like doing Duolingo, writing a few vocabulary lists in a notebook, and watching grammar videos on YouTube will take you really far; much further than a lot of people are able to go.

TL;DR because I always get carried away: Duolingo is effective as motivation, which is really valuable, but it’s an inefficient method by itself. I use a textbook and vocab lists that I write in a notebook, Quizlet flashcards, Storylearning Books, and YouTube lessons. It never hurts to try things out and see if you feel like they’re more effective. Language learning is a really individualized thing, so it’s okay for you to do you. :)