When dealing with C#, if you’re browsing code un anything less than a IDE it can be really hard to find where a symbol comes from. And that is if the author was nice enough to use one folder per namespace, otherwise it becomes a nightmare.
Although even source browsing is now easy - you just press F12, and packages come with sourcelink integrated automatically (previously you had to rely on IDE to resolve symbols or decompile it from IL (readable but not perfect, Rider did and still does it really well)).
Navigating the solution itself does not differ significantly from Rust and its crate system. People usually structure the code by projects and folders, sometimes aggregating multiple types in a file (because you don't need a separate file per a couple of 4 line class declarations) sometimes not but I generally find the structure way more browsable than e.g. what a typical TypeScript project looks like. The regular symbol navigation rules apply - F12, Shift+F12 and friends.
In Rust, Python and Go you can trace every symbol back to its source by just reading source code. `cat file` would suffice.
In C#, that’s impossible by design, as you say. C# imports work like wildcard imports in Rust and Python, which are wildly frowned upon for very good reason (except for specific cases like preludes in Rust).