I use over 300 hundred packages in my Emacs setup. I honestly not sure if I can install even half of that number of VSCode extensions and expect it to still run smoothly, maybe people do that, I just don't know.
They are called "packages" and not "extensions" for a reason - an extension that e.g., ships with a browser has limitations. In Emacs I can reuse functions of one package in another - in VSCode they have to be explicitly exposed via public API, must be activated in order, they need to be aware of their extension IDs, there's no discovery mechanism - in Elisp, I don't have to deal with any of that.
in Emacs I can explore, modify and bend the source code of any package - built-in or third-party. I can do it in a way that is simply impossible anywhere else. I can granularly change selected behavior of any command without having to rewrite it fully.
That "just works™" part I don't ever buy it - all software is faulty by nature. In Emacs, when something fails - I know exactly how to troubleshoot it, to the specific line in the specific package code; I can profile; debug and trace it. I can modify code in question in a scratch buffer and immediately check how it affects things. Not only I don't have to restart anything, I don't even have to save that code anywhere.
You call it "a legacy editor" without the slightest clue of what Emacs hackers are capable of doing - for what the most "modern" alternatives simply have no answers.
I agree, Emacs is not for the faint-hearted - many people (maybe most) lack the patience required to grok it. Yet make no mistake, those who have tamed this beast are not staying in it simply because "they don't know any better". They know - something better is yet to be made, if ever. VSCode is great, yet still not better.
Learning Emacs has liberated me from experiencing tool-FOMO ever again - I can switch to VSCode without abandoning Emacs, and I can even probably figure a way to control one from another if I get annoyed enough; I just never found a pragmatic reason to use VSCode more. So really, I have zero envy or crave to even become a full-time VSCode user; if anything, I might be forced into it by circumstances, but that's a different story.