Hynek is right,

setup.py

in itself was never deprecated* *although

setup.py

never gained support to declare the build system (PEP 517) and so having at least the

[build]

table in

pyproject.toml

has become a minimum requirement I feel **plus most people agree these days that

setup.py

was a big mistake and that project metadata should be declarative - folks could use

setup.cfg

for this but in the end

pyproject.toml

gained widespread support by all build backends (PEP 621) and that's objectively better than what we had before

***and finally