I'm incredibly thankful that Anki exists, I don't think I would have ever learned Japanese to a high level without it. But having spent some time looking at its guts myself, it sure is a mess in there. I thought at one point about building something on top of Anki, but decided against it discovering some of the same stuff that has already been mentioned.
The main Anki codebase is getting rewritten in Rust (from Python) so they'll probably clean up a whole lot of technical debt in the process and make future contributions easier.
I'm incredibly thankful that Anki exists, I don't think I would have ever learned Japanese to a high level without it. But having spent some time looking at its guts myself, it sure is a mess in there. I thought at one point about building something on top of Anki, but decided against it discovering some of the same stuff that has already been mentioned.