The way you've described both of those solutions demonstrates perfectly how C package management is an utter mess. You claim to be very familiar with the C ecosystem yet you describe them based on their own description. Not once have you seen them in use? Both of those are also (only) slightly younger than Rust by the way.
So after all these decades there's maybe something vaguely tolerable that's also certainly less mature than what even Rust has. Congrats.
You might be mixing up who you are replying to. I never claimed that C and C++ package management are better than what Rust offers overall. In some regards, Cargo is much better than what is offered in C and C++. I wouldn't ascribe that to a mess, more the difficulty of maintaining backwards compatibility and handling cruft. However, I know of people that have had significant trouble handling Rust. For instance, the inclusion of Rust in bcachefs and handling it in Debian that whole debacle.
They did not have an easy time including Rust software as I read it. Maybe just initial woes, but I have also read other descriptions of distribution maintainers having trouble with integrating Rust software. Dynamic binding complaints? I have not looked into it.
So after all these decades there's maybe something vaguely tolerable that's also certainly less mature than what even Rust has. Congrats.