My experience is, I gave up using clion on a pretty large c++ project ever since they moved to clangd (it used to be decent before) because some functions gradually became much slower to the point of being unusable, eg listing symbols in a file.

The same functionality works quite well in vscode.

But I tried this release and everything works really well on the same project.

This is a complete change of the language engine. The new engine brings many new features and correctness fixes, and it's additionally now running out-of-process, which should result in better performance.

Just doing some basic stuff between classic and Nova the refactoring speed is infinitely better. I'm not sure you understand the pain people have with classic