Is there any reason why these apps have to keep the database state locally? Why not just create a web service? The problem with this model would be keeping the server infrastructure running and getting some money to pay the bills, but it looks much simpler.

I also hate that the anki shared decks web site does not encourage collaboration, or at least not the decks I see in their web site. There are a lot of shitty, outdated decks and instead of collaborating to fix them people just upload their own shitty deck. Perhaps the people studying medicine who create decks on their own don't have this problem, but it is something I see in the web site. It would be great to have a site integrated with git so people can collaborate on github.

Also, classification of decks by language is something I miss. When you search for a language, eg. Russian, you get decks for English->Russian, but also for Russian->English. It's hard to find the deck I want

(Just some suggestions, in case someone of working on anki clones)