Rust does support C ABI through cdylib (as opposed to the unstable dylib ABI). This is used widely, especially for FFI. An example of this is Python modules in Rust using PyO3 [1].
Yeah but you can’t use the vast majority of crates that way. You have to create a separate unsafe C ABI, and then use it in the caller. Ergonomically, it’s like your dependency was written in C and you had to write a safe wrapper.
C++ has the opposite problem where people think they can just dynamically or statically link against any api be ok. You can’t cross the ABI barrier without a) knowing it’s there, and b) respecting its rules.
You get lucky when all assets have been compiled with the same toolchain (with the same options) but will lose your mind when you have issues caused by this thing neither you nor the package authors knew existed.