Dead cose in a huge monorwpo is more costly than just build and test time. It's also noise when searching through code. One thing to realize is that deleting dead code from the tree doesn't destroy anything because it's still in the repo history and can be restored from there.
Hence why Google has Sensenmann to reap dead code: https://testing.googleblog.com/2023/04/sensenmann-code-delet...
It's common to think monorepos are a way of shipping code. IMO, they're actually a mental model or model of your code and its dependencies. It's not just tooling for tooling sake, it gives you a new view into your code and its dependencies.
Holy fuck, this is great! Thank you!