Language requires repetition and prolonged attention to learn. Anki is good for sure but even with push notifications is not pushy enough to keep most people coming back to it on a consistent basis. Miss a day of Anki and now you're doubled up on cards to review next time which can disincentivize people from ever coming back.

This is where Duolingo succeeds and why it's valued so highly. Twisting dark patterns to the benefit of the user for a process that requires prolonged retention is the perfect fit. The techniques it uses are derived from research on how best to keep someone's attention. Saying they add no value to language learning and that people should pick up a textbook is essentially saying that you trust people to be self-motivated enough to stick to something like that for potentially years. That is a losing bet. I'd wager the vast majority of people would never be able to do it in their entire lives.

Anki doesn't give me push notifications on my phone to study every day. It doesn't berate me for missing a day.

It works for people who can stick to a schedule without pushing.