No, it can’t. However, it does have a value as an interest generator. The vast majority of people who start a language on DL, will stop doing DL pretty quickly. Of those who stay, there’ll be a percentage who continue using it for absurd streak lengths while never progressing past the point of basic comprehension or speaking ability. The remaining group will be a group who goes on to use real resources to learn a language the only way possible - through serious, disciplined, and often uncomfortable learning by immersion and real world practice.

I do think Duolingo has great value but I do think the second group I described is seriously wasting their time. I get it’s fun as a game but I figure you really might as well go all in with the amount of time a 1000+ day streak entails