1) it doesn't scale. You'll be overwhelmed with repetitions once you're in the high hundreds, and you will be if using Q/A style questions. And what's your daily strategy once it hits thousands?
2) I've converted all my notes from libreoffice writer to anki using python and various formatting tricks, and while the import outcome was perfect, most of the notes are useless - too ambigious/too broad/WIP - you'll never remember those well.
3) premade cards are mostly useless for long term - say you want to remember linux stuffs - you can find cards with thousands of items, but to what point - there's only so much time in a day and you want to learn something different than the author did - you def won't spend a year reviewing them.
I myself am confident this problem can be solved with supermemo and creating tailored q/a from my notes and thinking hard what I actually want to remember long term.