I'm not familiar with the JetBrains stuff, but I gather it provides functionality much like Eclipse does for Java. If that's the case, well I've been using Emacs for well over two decades and except for one abortive attempt in the mid 2000s I've never even bothered to use it for Java. The advantages of having a Java IDE that fully understands the code being written are just too great. The LSP is nice because it brings a kind of lowest common denominator for IDE style features to basically any editor, but I don't get the impression that it can match specialized IDEs.