You can do one thing in JetBrains: edit code. That's it.
In Emacs, I read my mail, I organise my agenda, I write technical reports, blog posts, I wrote my entire thesis in org-mode. I collect research notes in Emacs, and a journal. I do my bookkeeping and accounting in Emacs. I write Confluence articles, so I don't have to deal with Confluence's shitty interface. I edit remote files, I edit files via sudo on my machine. I control git. Yes, JetBrains can do git, too. My colleagues sometimes use it. Actually, they use an unholy mix of JetBrains, GitKraken and the command line on Linux, and Tortoise, SourceTree, JetBrains and the command line on Windows. Not different people. Everybody individually! Why? Because they know how to do different things in different tools. Meanwhile, I just use magit. Magit is absolutely fantastic, there is no better git interface, and I've tried many. Even for our backend Kotlin code, which I have to use IntelliJ for, I jump back to Emacs to use git, and edit yaml/graphql/etc files.
I've probably forgotten a couple of things here. And the cool part is that Emacs now supports LSP very well, and LSP is starting to support a lot of languages very well. So I don't even miss IDE features, such as refactoring. Add to that block selection, the best undo mode, actually robust modal editing (evil!) fantastic documentation, great flexibility, keyboard macros (I use them ~2-3 a week, and they're great every time)
… the list goes on. I've been a dev for less time than you have by about 6-7 years, but I can honestly say that no other tool could even come close to replacing Emacs.