Earlier quoted context omitted.
Emacs can do whatever you want. If it doesn't, it can be added. In fact, Emacs is an IDE... It's just not a mouse-based IDE. Mouse clicking makes my hands hurt much faster than using the keyboard. I also find it annoying to switch from mouse keyboard, so I don't want a UI that relies on constant mousing.
"Emacs can do whatever you want." 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.
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.