It's not an all C# project; C# only comprises the backend.
All in, the mono-repo is somewhere over 250k SLOC with mixed languages (Vue SFC, TS, Astro, JSX, shell). So when VSC is loaded, it's not only handling C#, but also everything else.
Point is that VSC is more than capable of handling production scale, multi-language workspaces even on 2021 hardware with only 16GB of RAM.
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.
VS Code starts out as a lightweight code editor & via extensions you can turn it into more of an IDE but it'll take a lot of customization & messing around.
Rider is an IDE with all the bells & whistles already included. It also has extensions but they've built it with the most popular things already.
Refactoring, debugging, code navigation, formatting & hinting/suggestions are far superior in Rider. They have a lot more advanced features. Check out some YouTube videos by JetBrains to see examples.
Don't get me wrong - VS Code is still a great tool & I use it daily. I do wish they would have named it something other than "Code" or "Visual Studio Code" but hey, it's Microsoft. They're famous for terrible bad name choices. Maybe they'll make a copilot to fix that.
Just my experience, but at multiple companies, which are in the 50-70 employees range, their C# codebases were over 1 million LOC and I didn't get the feeling that they were exceptionally large or doing anything significantly different. I would put 1 million LOC as "medium enterprise . NET" which would place 100k in the small or possibly medium sized if there was significantly more LOC in another language that is part of the project that you aren't counting (eg. different web front-end).
All in, the mono-repo is somewhere over 250k SLOC with mixed languages (Vue SFC, TS, Astro, JSX, shell). So when VSC is loaded, it's not only handling C#, but also everything else.
Point is that VSC is more than capable of handling production scale, multi-language workspaces even on 2021 hardware with only 16GB of RAM.