I moved to intellij because Eclipse's gradle support was lacking and people seemed to no longer care about fixing it to e.g. run bog standard Spring Boot projects. So yes I did move, and no I don't agree with you on this. And after years of using it, it hasn't gotten much better.
Intellij is and was a resource hog. And slow. It's a recurring topic in the Intellij release notes. And it did get better over the years. There are numerous open/unresolved issues in their issue tracker related to all sorts of performance issues. No need for me to file new ones: they know. That's why they keep trying to fix and improve it. But the proper fix is going to require doing what Eclipse did two decades ago, which would be a major architecture change. I don't think they'll ever do that for Java. They might do that for Kotlin though as that is a compiler they've built. Not doing this from day 1 with Kotlin was a design mistake IMHO. But they are working on a more IDE friendly Kotlin compiler.
I've actually demonstrated how slow intellij is to people who told me I was crazy. On their own supposedly heavily optimized setups with their own projects. Edit some code, run some test. Eclipse: no delay whatsoever, test start running immediately. Intellij: it takes at least a few seconds before anything happens. That's the best case scenario. Change even one letter in the code and now it "incrementally" compiles, which in Intellij means firing up a gradle process. In Eclipse, the process already runs. It picks up the change immediately and then the single file that you changed is recompiled. It could even do this on broken code. So you could have compile issues in the file and still run a unit test against the non broken parts. Partial and incremental compilation are hard problems to solve. Eclipse had this, Intellij does not. It does some incremental stuff via gradle. But that takes a lot more time. About two orders of magnitude more. Even on a new M1 macbook pro.