My experience with language servers in VSCode has been less than stellar (looking at you Golang integration).

I just haven't found anything as responsive as IntelliJ's custom embedded autocomplete/code-formatting/refactoring capabilities yet... everything else is just inferior feeling.

I never had much success in setting autocompletion in Vim. Jumping to symbols somewhat works but since the editor itself is not build-aware it always gets thing like include paths wrong. Maybe with editorconfig.json or something it would work better, but in the end I found completion in dedicated IDEs always much better.

Language servers are supposed to mitigate that - they're supposed to be build aware and know all about include paths etc. For the C family this is usually done by having CMake write out a compile_commands.json file as part of its configure step, which is then picked up by the language server. Other languages should have their own methods. I still use build-unaware indexing, i.e. ctags, because it's simpler, faster and lets me look up things that aren't part of the current build configuration without having to switch builds.