It's not that VS Code can't load a large project, that is table stakes. It's that the tools it provides to work with those large code bases are like fisher price versions of the Jetbrains equivalents. If one take their tools seriously, and uses them to the maximum extent possible to increase productivity, reliability, and robustness of code then there is just no comparison between the two.

Don't get me wrong, I still use VS code for all front-end development and other ecosystems (such as Rust). But when it specifically comes to C#/.NET there is no substitute to Rider in my opinion.