Jetbrains IDE's definitely aren't slow. You need to change the default memory heap sizes.

Same codebase loaded up in Webstorm vs VS Code and I can't see any difference.

Webstorm took about 10-20 seconds to index it but their implementation of the AST is unbelievable. So much more powerful than VS Code. I get code completion in way more places than VS Code and even when they both provide options Webstorm takes the local context into account and much more accurate than VS Code. Refactoring is breeze.

There is no comparison. I happily pay the initial load up time in the morning for smoother ride for the rest of the day.