I have come to the conclusion that shared decks don't work, at least not for me. The reason is that actually assembling the deck has turned out to be almost as valuable as practising with it.
I've got well over 1,000 cards in my Indo deck right now. I had to go find every translation and decide whether synonyms should be on the same card. That activity produces its own kind of learning.
For medical students, there’s a fixed number of study resources that create a shared knowledge context for everyone using them. Anki decks are created from these resources and shared. In this case, shared decks are actually useful, high quality, and closely cover the material.
It’s much more efficient to use these premade decks - in the time it would take me to create one card I could have reviewed 5. If you have high quality decks, you can really optimize time spent on active recall by doing flashcards.
But Anki makes up for that in consistency. I went through a deck of about 8000 cards and it was tremendously valuable. I could’ve learned the material faster with other methods, but only if I had the commitment to it. By contrast, opening an all every day on the train is a breeze.