setuptools itself doesn't have to - install package dependencies, create a lock...

@keul setuptools itself doesn't have to
- install package dependencies, create a lock file (python setup.py install)
- act as a place to put build tasks (python setup.py tests)
- bump versions (setuptools_scm)
- build pure python packages

That leaves native code interop. You can't do cython, mypyc without a setup.py file.

Many of the best improvements to setuptools has been to discourage people from using it to install deps, run tasks. If only they could go all the way.