In Emacs, I can feed the word at point to a bunch of local and online services and show the results in a single buffer, or insert them at cursor, or export to html, pdf, etc., or automatically send somewhere, or print. It would take me a few minutes and probably no longer than a dozen of lines of elisp. I wouldn't even have to save that code. Or restart Emacs. Or install any additional plugins that would require me to restart it. I wouldn't have to write code from scratch if I could reuse existing plugins. I can even suppress their desire to display things their way by tapping into their internal functions and force them to run my code instead. Which of that is possible in IntelliJ?
Having a similar feature "like in Emacs" doesn't make it exactly as powerful as in Emacs. In order to understand what makes Emacs so extensible, first, one has to grasp what makes Lisp so flexible. But that's a conversation for a whole 'nother topic.