A gui is a nice way to make a lot of functionality discoverable.
But it is easily discoverable ?
I literally just do M-x and can I get a buffer open with _all_ emacs commands and their explanation, and can do a fuzzy search on that, e.g., so if I type "M-x align re" I get only one command highlighted that can just execute "align-regexp".
That's the main thing I like about emacs. I don't have to remember a million shortcuts, just what things are possible, and then I just type a description of what I want to do and hit enter and that's it.
A GUI / having to use the mouse would push me completely out of "the zone".
Emacs tends to have its own names for many concepts, making things even more obtuse.
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.
In emacs I can use "apropos" (i.e. "c-h a") or "c-h v" for example to search for ways to accomplish what I'd like to do.
I just yank into a new buffer, set it to xml mode, "M-x indent" reveals the command to format xml (indent-region or indent-buffer or something like that), enter, yank it back. Done.
In an editor with a gui, I would just go to "Help -> Search" and do pretty much the same, which would reveal the menu item to click to achieve something. I find emacs ido/helm workflow for this much better. Never need to memorize anything.
These helps are also available in the GUI menu bar, for example Help > Describe > List Key Bindings, which also mentions the keybinding `C-h b` to the right of that.
How is discoverability of keybindings lacking?
A GUI also introduces other problems, but the ability to just point at what you want to know more about or do something with has been a cornerstone of discoverability since the introduction of the mouse.
transient-mark-mode just allows you to see what you're selecting. If you don't have it you don't see what's being selected until you release the mouse. You need that more with a mouse than a keyboard.
Yeah, no. It's a modal state, and since Emacs doesn't support modal interfaces directly, it touches tons of separate commands (anything using `region-active-p`) and means it's tremendously difficult to find out all it does!
Many commands change their behavior when Transient Mark mode is
in effect and the mark is active, by acting on the region instead
of their usual default part of the buffer’s text. Examples of
such commands include M-;, M-x flush-lines, M-x keep-lines,
M-%, M-%, M-x ispell, and C-x u.
To see the documentation of commands which are sensitive to the
Transient Mark mode, invoke C-h d and type "transient"
or "mark.*active" at the prompt.
But I'm no expert!
Try explaining "yank-pop" to somebody who's only ever used sublime/vscode.