“If you need a dedicated tutorial for a text editor it's a great sign that something is very wrong with its design, particularly concerning discoverability.”
I don’t agree. If it was a mass-market product for users who just wants something convenient, then I would agree. Those users are probably better served by other applications. (Word, Evernote, OneNote, Notepad++ etc etc) But Emacs is a power tool for power user. Therefore I think it’s okay that it needs a tutorial to get started. You need to invest some time to learn in. That will, in my experience, pay off greatly in the long run.
Let’s take an example from another domain:
Suppose someone wants to get started with 3D Graphics. I’m pretty sure software like Blender and Maya also needs some kind of tutorial in order to be useful.