It's true that some things are lacking, so it's too bad that whoever wrote the code that does your high-level syntactic analysis didn't make it independent enough that it could be used in other places than whatever IDE you were referring to.
Yes, I've used ctags and I've used etags. They tend to be interesting approximations but are never 100% reliable. They don't do a deep sematic analysis of my program. (For example, they don't understand C macros.) They don't update as I type.
The closest I've ever seen has been the "Semantic Bovinator" thingy. I have never managed to get it to run, nor has anybody I've seen try. You experience may be different, of course. (I realize that by posting this I'm inviting a raft of people to post and say "It works for me!" :) )
SLIME has this in Emacs for Common Lisp and perhaps other languages that work with SLIME.
I'm on a non-multitasking phone now so you'll have to do the googling yourself.
We might use different technologies. I mostly write Objective-C, Ruby, Python, C, JavaScript, and recently some Objective-J and Erlang. Now and then I write Lisp (CL, Emacs), Scheme, Haskell, x86 assembly, and PHP. The only one of those I don't write in Emacs is Obj-C.
Other editors or IDEs may be better at certain tasks, just as Emacs has unparalleled Lisp support with SLIME. When there is clearly a best tool in one field then people tend to use that tool, if the payoff is worth it. Except for pg and a few others, people generally write Lisp in Emacs. I write Cocoa and Cocoa Touch apps in Xcode and IB. I'm pragmatic about it. But when I tried to use Eclipse for Mojo (webOS) because Palm recommended Eclipse + Mojo plugin, it ended up being more productive for me to extend an existing Mojo mode for Emacs[1] to have even more features[2] than the Eclipse plugin (or any of the others, Komodo, etc). Similarly if I were doing Java I would at least look into IntelliJ IDEA or Eclipse.
[1] http://www.emacswiki.org/emacs/MojoSdk and http://github.com/samsonjs/mojo.el
[2] http://www.webos-internals.org/wiki/Comparison_of_Editors (temporarily down)
Perhaps vim and emacs don't do everything you want. But also, perhaps you don't know their capabilities as well as you think you do?
That said, I use vim for C, but I still use Eclipse for Java and C++/Qt.
Saying "Emacs can do whatever you want" is like saying "your computer can do anything you want." Sure it can, so long as you're willing to write the code to make it go. But my time is finite; I cannot be bothered to re-build environments that have already been implemented elsewhere.