The only reason we use pyproject.toml is because of the stupid black formatter that refuses to support setup.cfg, which every other python tool under the sun supports.
Yeah, it's annoying. But Black has so little configuration that I'm ok with hardcoding command-line parameters in my Makefile/tox.ini/precommit hooks (`--skip-string-normalization --line-length 79`)
There are other formatters, some may even be better.