Duolingo is a good tool for stuff that flashcards are good for - learning letters/alphabets/symbols, learning new words, basic sentence structure/grammar, etc. It’s one good tool for language learning, but it won’t do the whole job by itself. Certainly not garbage, as long as you use the tool correctly.
If you really want to learn a language ditch this garbage and try comprehensible Input.
Duolingo is a good tool for stuff that flashcards are good for - learning letters/alphabets/symbols, learning new words, basic sentence structure/grammar, etc. It’s one good tool for language learning, but it won’t do the whole job by itself. Certainly not garbage, as long as you use the tool correctly.