Emacs arguably is the only one of the true meaning of "Integrated Development Environment" perhaps more thoroughly than any other editor. When we break down what IDE really means - integrated, development, and environment - Emacs excels in each dimension: it deeply integrates every tool and workflow through its unified Elisp ecosystem rather than merely bundling separate applications;

I can start extending it on every possible dimension without even having to write any code into a file - I can open a scratch buffer, write some Elisp and evaluate it in-place.

What else can provide a complete environment where one can code, debug, manage version control, read documentation, run terminals, manage projects (I search through Jira in Emacs), and even handle email or browse the web without ever leaving the editor? I'm reading this thread and typing this comment in Emacs, btw.

While modern "IDE"s like IntelliJ or VS Code offer polished, pre-configured experiences for specific languages, Emacs takes integration to a philosophical level where everything shares the same keybindings, configuration language, and conceptual model, making it less of an application that integrates other tools and more of a platform where all tools become native citizens of a unified computing environment.