I've got a whole labouriously created setup for my emacs that is roughly equivalent to my RustRover setup in terms of capabilities (though not [mostly] in terms of keybindings because my fingers are fine with default emacs bindings). And I still barely use it, and I continue to fire up RustRover constantly.
Because it just never feels snappy and fluid and responsive and stable. RustRover is a slow dog at times, but even it outperforms emacs for a lot of things.
The lack of proper multithreading in GNU Emacs is a problem.