Well I suppose that's what I'm asking, is that the case? I'm not aware of other projects that have a separate plug-in due to LSP shortcomings, so just interested if there is something they're doing that's not possible/won't be in the LSP one.

I think the answer to your question is yes: LSPs can’t do everything that a plugin can do.

https://blog.jetbrains.com/platform/2023/07/lsp-for-plugin-d...

That sounds like a limitation on Jetbrains part, no? Or is it due to LSPs themselves?

I suppose there are things which are just beyond the scope of LSP, like menus and other UI bits which are IDE specific, not to mention refactoring tools etc.

That would be on the client (the LSP support in the specific IDE) to implement though, and would then work for any language server that implemented those capabilities?

Like 'go to definition' or whatever is surely in every IDEs menu, but it can be done with LSP.