edit: And there's nothing wrong with key bindings being 30 years old, Vim for instance has an incredibly efficient interface. Also, I find knowing basic emacs bindings quite useful around the OS X interface (many of them work).
(I know some people like to shake themselves up by doing the text editor equivalent of putting their shoes on the wrong feet, then once they get used to that, switching to walking on their hands to stop themselves from getting too comfortable - but I'm not one of them.)
IDEs come and go. Emacs stays. It used to be mocked to be too large, today it's an average package, and tiny compared to other IDEs. It does a lot and let you extend it very freely (as of 2008, doing anything in Eclipse was a burden, can't speak of todays state though, I'll add that Emacs cruft has nothing to be ashamed of to the Eclipse Plugin and Workspace model, hundreds of (Object) list.get(arbitrary-index), TIMTOWDI.. )
People drool over features that were present in emacs for decades (flex match), and I've seen emacs absorb new ones (in-place evaluation of code with value preview for instance) faster than I would hope (a few years ago, a 2h sublime demo had literally nothing special).
It's syntax system felt (I never looked into it) superior to Eclipse (except for JDT) and VS.
Also Emacs users have a way of doing things. No mouse, often very lean. I'll rant about Eclipse again, but it really is bad. My hands hurts after one day (I morphed into an emacs alien maybe). Git integration is between unusable and useless (after 10y+ of work). etc etc
Plus energy is still flowing, look at Spacemacs, it's a lot less absurd than emacs, with a more stable plugin mechanism. People are still working on bringing guile elisp mode as the base vm.
Emacs have a lot of issues, and they don't matter.
https://www.dropbox.com/s/e6vhweatnrb98ow/spacemacs.png?dl=0
Are you _sure_ it is something usable? :)
On my MBP and the ones of my colleagues, plus my windows machines, spacemacs works great and without issues the last couple of months.
It even convinced 10y+ vim and IDE users to jump ship after testing it for a week.
From my own experience: developing in go, elixir, javascript + react ... It feels exceptionally great with the correct "layers" installed. And being a top notch crosslanguage IDE is just the tip of the iceberg of what spacemacs/emacs actually is capable of...