No, it is because Duolingo is an addictive trap optimized for "engagement" (not learning) that requires you an absurd amount of time to progress very little, because it is explicitly designed to be ineffective with the looks of being effective (that's how they make money).

Want alternatives? Among apps, LingQ, for example, or LanguageTransfer. Among not apps, Lonely Planet phrasebooks and StoryLearning graded readers.

There are really many good options if one bothers to search.