Just as an example: I learn languages using Anki, and I always do it the same way: I use decks that

* exclusively quiz entire sentences

* introduce around 500 new words (a nice mix of nouns, verbs and adjectives)

* use a wide variety of grammatical constructs (including all conjugations of the new verbs),

* and that have audio of a native speaker reading the entire sentence after I "flip" the card

Such a deck needs to be thoroughly designed, and while I could choose the new words and then write software to make sure they are all used equally in sentences and no conjugations are missing, I actually can't easily make sure they are correct and I can't record the audio of the text.