I tried the LSP-based Java extension for VSCode on a large project (~2M lines, large Gradle build) and it was unusably slow. More than 30s for a "Go To Definition" command with my CPU pegged the whole time. Caveats: It's possible the VSCode implementation was bad, but I think it was the LSP, and this was a few months ago, so things might be better now, but it would need to have orders of magnitude of improvement in performance to be tolerable.

IntelliJ handles this project pretty much without breaking a sweat.