Terminal editors generally do support the mouse, and there are occasions where even a fairly skilled user of a good terminal editor will find it easier to click to set an insertion point than use commands to reach it. But having those key-command options greatly enhances the experience. You need to watch the screen while a skilled user edits text to get it. It's like magic.

I haven't picked up nearly as much as I'd like, but even basics (requiring zero config) are way beyond what I could easily do in any GUI editor I ever experienced. For example, in vim, if you are on a bracket or parenthesis (open or close) in edit mode, it is three keystrokes to delete the entire bracketed portion, precisely, regardless of size (even if the matching bracket is off screen). Finding the matching bracket with the mouse is often hell.

And it's not as hard to learn as you may expect, because those keystrokes are not magic codes; they're part of a consistent, thoughtfully designed command language. You choose a mode for selecting text (character based, with lowercase v), use "motions" to select the text in that mode (in this case, a single "go to the matching bracket" motion, which is the percent sign), and take an action with that selection (delete it, with d).