Like everything, IntelliJ got increasingly bloated, at a faster rate than the progress in CPU performance.

I've got a desktop machine from around 2010 with 32-bit OS, Core i5 760 (510 / 1611 point in geekbench single/multithreaded) and 4 Gb RAM, runs my current Java code in IntelliJ from those times at blazing speed. Modify a line of code and run in debug, it's up an running in less than a second.

Same code on a 2018-ish laptop, 64-bit OS, 16 Gb RAM, i7 6700 HQ (798 / 3073 in geekbench) and latest IntelliJ takes up to 10 seconds to start.

It's not "Java", it's bloat.

C++ ides do cache files and monitor for changes too but they are much more useable on low-end hardware than anything Java.

Citation and meaningful comparative ananlysis needed here. I would want to be certain you are not making a comparison with powerful text editors like Slickedit or Emacs - these are not the same.

At the scale that something like IntelliJ or your favourite C++ based IDE operate at, Java is not the bottleneck. It’s all down to the system complexity involved in doing all that code crunching in near real time and the integration with various back ends and plugins that causes the lag.

I have used many a native IDE in my time and they’ve all been pretty horrid, and to me Intellij is probably the best of them. At this scale of complexity I think the tightly structured and predictable environment provided by Java actual helps performance as it’s easier to maintain and design a cohesive scalable application.

I'm mainly using Qt Creator, which has integrated on-the-fly code analysis with clangd for instance and I guess most of what you'd expect from a modern IDE, many refactorings, various unit test system integrations, SSH support...

When trying CLion on the exact same projects everything is just so much slower with no major value-add, like, even opening UI menus feels sluggish. And let's not even talk about typing text, I feel like I'm fighting my keyboard whenever I try to use it. (My computer is an Intel 6900k with 64 GB of RAM to give a point of reference)

QtCreator does a tiny fraction of what Intellij is capable of though. Also, clion is not nearly as used as intellij, which is (only slightly arguably ) the best ide hands down for java and many other languages.