Can someone please explain to me why I should learn vim? I've made several attempts in my lifetime because I thought there would be some magical "ah-ha" moment, but it never came. Separate modes for command & insert just feels inherently clumsy and slow to me. Is there some other killer feature that can't or hasn't been reproduced by modern editors?
What's more, as several other commenters have alluded to, vim thinks of editing as a language. There are verbs like cut or copy or paste, and there are nouns like [this] sentence or [this] word or one word backwards or from here until the letter j. Once you start building sentences of editing commands (e.g. copy from here to the 3rd next instance of the a line starting with 'Hello' namely ) the flexibility it offers is unparalleled. This is all done from your default context without fingers leaving the keyboard. Once you achieve fluency (admittedly not a trivial task) there is no context switching for any editing task, it becomes reflexive and subconscious.
Other stuff, like macros and registers, or easy access to regexes and ex commands help extend this, but the core reason why vim is still used today is this strength.
I'd highly recommend another classic response, given here, elaborating on the nature of vim as a language for editing: https://stackoverflow.com/questions/1218390/what-is-your-mos...