Any place which has internal tooling tightly coupled to Eclipse, and isn't willing to or has not gotten to develop the same for IntelliJ.

Speed in large projects. IntelliJ is super slow once you have huge source/text files. E.g. WebStorm is unusable for debugging as one step over takes ~10s on a 128GB RAM machine in such cases.

I am mentioning this in the off chance you did not tried it, exclude the node_modules/vendors/build folders or other third party code that is not part of your project you are editing.

It happens also in own projects that are just huge, without any 3rd party libs.

I am not experiencing this issue and I have a large project PHP and JS plus the plugins for jquery and angular , all linting on. After the project loads I don't feel any lag, I run an i5 6th gen CPU , 4cores. I might have tweaked some VM options years back (my configs and styles are at least 5-6 years old so I do not remember).

Also if you transpile all your js into a big minified file, exclude that too, right click on it and there must be an option as mark as plain text.

this sounds like a good candidate for issue report. Would you mind collecting performance snapshot and sending it to JetBrains?

Because of Eclipse RCP or EMF legacy?