I don't immediately follow how Rust breaks the ecosystem. Rust has very good C FFI support and fully supports the default C ABI. It just requires unsafe bindings.
In practice, my Python packages broke when they dropped the C crypto support. I'm sure it was theoretically possible to avoid that, but they didn't. And that's ecosystem breakage. (And if the fix is that I the user must go manually install or worse compile extra things, that's definitely ecosystem breakage)
TL;DR: Look at it from our perspective. It's not reasonable for us to be beholden to the limitations of build targets we never consented to supporting and possibly didn't even know about.