> Cargo is very opinionated, forcing upon you certain directory structures

No, it expects source code in `src` like most C/C++ projects anyway. Then it's `lib.rs` or `main.rs`. The opinionated directory structure (`pkg.rs` or `pkg/mod.rs`) is rustc not cargo.

> even a default VCS

Because it's the one used by most projects. Anyway, nothing prevents you from using mercurial, svn, ...

> Building multiple binaries and libraries from one project is a pain

Have you heard of Cargo workspaces? Because I've had no troubles with it.

> I think `gcc app.c` is way easier than using cargo

Agree to disagree. Because really soon, you'll want to manage dependencies.