[knubie]

I had the same thought and created my own implementation [0]. As another user said it's surprisingly difficult, and Anki is incredibly extensible, so it can be difficult to fill everyone's need.

What I've noticed is that a lot of the power users and influencers are very much invested in Anki, which makes it difficult to get them to check out your alternative. And because these are the type of users that are promoting Anki, it has gained a lot of mindshare in this space.

That said, the people that have found my app are very grateful it exists as an alternative to Anki.

As far as the syncing, as another user said, it is actually quite difficult. There just are not a lot of options out there for this kind of use case. Anki's syncing is custom-built.

[0] https://mochi.cards/