You can do all of the above with Wheels.
Arbitrary examples, I know, but I moved a large software that was truly mixed C++ and python project to conda-forge and all sorts of random C++ dependencies were in there, which drastically simplified distribution and drastically reduced compile time.
If I had done it today, it might be nix+bazel, or maybe conda+bazel, but maintaining a world of C++ libraries for distribution as wheels does not sound like fun - especially because nobody is doing that work as a community now
Conda is like Jquery or Bootstrap: It was necessarily before the official tools evolved. Now we don't need them any more, but they still are around for legacy reasons. You still need it for example, for some Moleular dynamics packages, but that's due to the package publishers choosing it.