For example, everybody was kind of 80-90% on syntax highlighting. Some editors and IDEs were a little better at one language than others, but most weren't that great and had all manner of weird edge cases. And, if you wrote a new language, good luck because you had to write a syntax highlighter for it in both emacs and vim to get traction.
And then VSCode came along with the Language Server Protocol. Suddenly, you only needed to write a well-constrained plugin to get your syntax highlighting to about 80%. That was okay.
But the modern languages learned from the failures of C and C++ and designed themselves to be parsed quickly and accurately. So, now your LSP syntax highlighting could go to roughly 99% accuracy on VSCode. And the highlighters were incremental. Suddenly there was a genuine advantage to using something other than emacs.
And this is before we get to things like a debugger that works, etc. I've used all the IDE's, but VSCode is the first one to pry emacs from under my fingers.
And for people who like to complain about VSCode and Electron bloat (a valid complaint), I'd like to point you to some of the old nicknames from the emacs vs vi religious wars (Eight Megabytes And Constantly Swapping springs to mind ...) Bloat simply isn't an argument for most people.