Emacs is vast and deep and there's a lot to learn and remember.
It also serves the same purpose for key-bindings and functions in various modes and packages.
That’s not silly at all, a lot of people use Anki for things like that. I’ve seen a couple of premade decks but I would avoid these.
When it comes to keybindings its better to make your own deck otherwise you end up learning a load of bindings you’ll never use. I like to add them as and when I need them.
It's not always that easy to find - even with C-h a or C-h m, etc.
But the bigger benefit is even knowing that feature X exists and there is a key combination for it. I found flash cards useful because I would get an occasional "reminder" that X exists and I should use it more often!
A trivial example: flush-lines and keep-lines. I never knew these existed till I read them somewhere. I put it in my flashcards, and over time I would remember its existence and use it more and more.
You could also try searching for "apropos" with apropos-command to find other related commands.
Seconded on all counts! Ruthlessly delete cards you don't care about; make your own cards so that they reflect your own mental structures. In the article, I allude to this by talking about how people can undergo very different mental motions to obtain the same "serialised" fact like "78% of the air is nitrogen".
Suspending on the other hand, takes the card out of rotation, and if at some future point one cares about the card again, it is easy to unsuspend.
What’s that you say? You downloaded premade decks? Don’t do that! Constructing your deck yourself is an important part of the learning process.