Emacs is special regarding UIs

Emacs has the idea of _buffers_ which are the actual window panes that you can view. The _buffer_ has data in the form of text which has properties in much the same way a block of html can have properties. An emacs-lisp function has full access to do anything it wants with the buffer. For example it can insert contents, change the font family, change the bit of text into a button with a callback. This is exactly how syntax highlighting/semantic highlighting works in emacs, you just change the styling for bits of text [1].

A _mode_ inside emacs is a collection of emacs-lisp functions which trigger (usually on a file extension name). Typically they will set certain keybindings for specific mode-like behaviour. You always have a single _major_ mode and multiple _minor_ modes - the vim emulation layer, for example is simply a minor mode which adds the vim keybindings and emulates the vim state machine inside emacs-lisp.

> It seems like each script is registering commands it can run in context of mode

An emacs-lisp file can be _evaluated_ in the same way as a python file into emacs. It's like a REPL - you can evaluate a file and the functions become available. There's a bit of extra behaviour which allows lazy loading et cetera, but user defined scripts are first-class and there's no distinction between them and those which are "native".

> updating of values

You can update a variable by simply evaluating the appropriate lisp function. If you want to update a value in the text buffer, you just replace/rerender that chunk.

> handling async requests

A buffer can also have a _process_ running which gets events each time the buffer is updated. When you run a command, you direct the output to a buffer and you trigger your lisp function on certain events. This is sort of how the HTTP requests work, but there's libraries which abstract some of it for you. Buffers are really just an abstraction for textual data.

Some of this is simplified, but I hope it gives you a vague idea of what emacs is.

[1] https://www.reddit.com/r/emacs/comments/iemo44/wysiwygified_...

For one, all the keyboard shortcuts and commands that you have to learn; I don't know if I have the capacity to learn all that anymore, not without deliberate practice, while in modern editors you can get by with keyboard + mouse and slowly learn some new shortcuts here and there.

Second, it feels like you have to spend a lot of time to set it all up.

Third, will it replace an IDE? Error checking / linting, autocomplete, fast navigation, auto-imports, loads of things like that that seem to just work out-of-the-box in e.g. idea.

no

As an example, these days, when routing PCB tracks in KiCad, when I need to switch to a different board layer, I need to look away from screen and at the keyboard in order to hit the right function key. I also have to pray that the TouchBar will register my press, as it often likes to go to "sleep". I don't know if it did register my press until I look back at my screen and check if I'm on the right layer.

Having to look away from the screen when you're in the middle of routing a track on a complex multi-layer board is really annoying.

Plus, it's difficult to keep a hand near the function keys without accidentally getting near one of the touchbar areas, which results in a keypress, which results in a zoom-out for me (F1).

It's an abysmal user experience and a huge regression.