What in particular did you find wrong?

@@UXDX. Duolingo is a prime example of "what you measure is what you'll get". They're not measuring "learning" and "language skills", but rather optimise for "engagement". Speaking from my point of view, the end result is that me and everyone I know who's used it at best only learned some vocabulary and a few phrases, after using it daily for months. We stopped learning the content, and instead only memorized whatever was necessary to finish a level. Of course as a business, engagement trumps almost anything else.. The idealogy of data-driven decision-making is apparent. She often concedes that they don't know the real cause of behavior changes. They simply try to maximize their KPIs of retention, engagement, etc, like you would when studying a mice in a lab. Main takeaway: don’t do data driven design if you don’t even remotely understand why the data happens. If you base your decisions on -0,5% metric which you can’t even explain, that’s just absurd.

@@amnezija I literally laid out my reasoning but ok