Rust-Analyzer is much better than whatever IDEA/Clion uses IME.
Is there anything other than performance and proc macro compatibility that RA has over IntelliJ-Rust? All of the alternatives to IntelliJ-Rust are just missing critical (to me) features like refactoring.
RA uses chalk [1], which is a trait solver rewrite for rustc. You can already use it on nightly with a feature flag.
So RA can get close to the trait resolution of the compiler, which is probably the most challenging part. I haven't used Intellij in a while, but I doubt they can ever get close with their custom implementation. I always had trouble with trait resolution/autocompletion, which is often where you need from the IDE the most.