Logical and human friendly answer: mutable objects are not a problem, poorly designed code is

Personal rant: why even bother with objects, just use strings, ints, floats, arrays and hashmaps (sarcascm. I have spent hours uncovering logic of large chunks of code with no declaration of what function expects and produces what)

And also, seeing endless create-object-from-data-of-other-object several times has made me want to punch the author of that code in the face. Even bare arrays and hashmaps were less insane than that clusterfuck

I keep hearing about how modal editing is faster

Please, do yourself a favor and ignore that noise. It is more a question of like/dislike and training. Personal sidenote: I daily alternate between PhpStorm and Neovim. Can’t say doing things in either is faster/slower to any significant degree (PhpStorm is mostly there for the things I have not yet configered properly in Neovim, like looking through git history)

and I would like to switch to a more performant editor

This should be looked at and tested objectively: is it working with big files that is the problem? Or navigating the code base? Or something else? Maybe it is better to tweak vscode instead?