Duolingo simply does not work for actually learning a language. It's better to use something where you practice immersion learning, preferably with other people and there are apps for this online too.

It sure does a little bit, but a) quality varies a lot - some courses can get you from zero to dos cervesas por favor, some are just poorly structured noise that has no chance of sticking in mind; b) doesn’t explain grammar (it’s an exception when it does), so results greatly vary on preconditions like languages you’re already familiar with and can relate - anything too foreign and you’ll have hard time trying to understand how those examples generalize.

Duolingo it got me just enough Spanish (with zero prior knowledge) to get around, communicate basic needs (like a caveman, sure) and understand simple instructions, all without putting serious effort to learn language properly (putting serious effort into it) but only casually, as a side task.

Duolingo does work for those A1-B1 levels it has courses for. At minimum, it got me where I was able to switch to netflix.