I just can't live without a core thing like this missing, and compounded with a number of other things that Eclipse does better, I stay on Eclipse. Unfortunately many younger developers think IntelliJ is all there is.
Given that performance is a recurring topic in the Intellij release notes I conclude that they know they still have issues there and they are slowly looking for ways to make things faster. This is not a solved problem.
Part of this is the Kotlin compiler; part of this is indexing; part of this is simply caching logic.
I recently worked on the Elasticsearch code base in intellij. Fast is not a word I would use to describe that. It's a big code base and it clearly was struggling with it. I know some Elastic developers that still use Eclipse basically for this reason.
Before that, for doing vanilla maven + Java projects Eclipse was awesome and generally running circles around intellij in terms of performance, which is still something that is off by order of magnitudes in Intellij and something I miss a lot.
Intellij users are always surprised when I bring that up and say it is fine on their machine. And then I point out that 5-20 seconds to run a unit test after a 1 letter code change is obscenely slow compared to Eclipse because it finishes incremental compilation a few ms after you lift your finger and is ready to run your test. Intellij attempted to integrate the Eclipse incremental compiler but it is not used by default and generally not that well integrated. Their compilation strategy depends on a lot of caching, which is hard and frequently gets in an inconsistent state (i.e. your IDE lies to you about things compiling or not compiling), which is why people routinely rebuild their whole project, or worse invalidate caches and restart (a top level menu option because it needs to be).