Would it be better if memorisation could be achieved through distributed practice, vocabulary learned through reading and listening, spaced repetition achieved through well written textbooks, curriculum, mentorship, etc? Absolutely, but these factors aren't always a given and often are often outside of one's own control. If failing to keep good Anki hygiene is considered in the ROI calculations, these issues should be included to.

Maybe your textbooks just don't distribute problems well enough, the curriculum changes drastically such that what you've just learned isn't touched on again before you forget it, or maybe you just don't have the time or material to consistently practice foreign languages for 1-2 hours a day. In these cases, the 10-20 minutes spent reviewing cards serves as a useful crutch in preventing that information being forgotten entirely, which undoes all the time spent trying to learn it in the first place.