> What's the upside to Duolingo? Is there any, whatsoever?

Uh, it's easy? You install the app, select the course and just start learning pretty much immediately. It got me from "I want to learn japanese one day" to actually learning japanese.

I really have no idea why people are so skeptical about duolingo. Nobody's claiming it should be the only resource but claiming it provides no value whatsoever is just false.