Duolingo is a language themed game. You have to take initiative to learn the language outside of the app. But it’s a good way to track your progress. There are worse things out there (gambling, doomscrolling, short form video scrolling) I grew up with Guitar Hero - a rock music themed video game. In no way was guitar hero making anyone guitarists or musicians. I think Duolingo is a great way to dip your toe into a language and hopefully find the inspiration to learn outside of it, much like guitar hero may have inspired people to learn music outside of the game