In about 70-80% of the cases, using ido or helm, with some guesses on what the command name may contain, is enough to find me what I need.
But yes, to be frank, my productivity in Emacs really took off once I started memorizing things with flashcards. I currently have 603 cards for Emacs (including elisp).
(And telling a newbie that would cause a lot of despair!)[2]
The other thing that really helped is I started using/making hydras.[1] So now when I encounter a new, interesting mode, instead of memorizing lots of command names or keybindings, I just build my own custom menus.
[1] https://github.com/abo-abo/hydra
[2] But it really shouldn't. Emacs, with all its packages, and modes, is like a language with all its libraries, and not just the standard ones. Remembering all the commands/keybindings is akin to expecting someone to know all the APIs in all the libraries. It's OK if you don't. Most people don't.