I'm a MERN Stack individual developer. Visual Studio Code auto complete recently started to function poorly, especially with Node.js & Mongoose, and that's why I'm thinking to move from my comfort zone. Do you have any recommendations for me? I have a weak device, MacBook 2011
Before getting rid of Visual Studio, I'd recommend looking at the extensions you installed for it and try disabling some to see if those could be the cause of your performance issues. The same goes for your O/S as well. I doubt that Eclipse will be any faster than Visual Studio. Not sure about Webstorm. You can always try Atom or Sublime text, which I've tried several and decided on Visual Studio Code.
Since you are used to with "modern text editor", and your device is pretty weak, I recommend Sublime text and Vim. Maybe Vim is hardcore choice but it's worth have a look. Safe choice is Sublime with extensions installed. Drop VSCode or WebStorm if you don't want to kill your device