Earlier quoted context omitted.
I don't have any issues with Python's packaging ecosystem anymore, having settled comfortably into a pyenv+virtualenv+pip-tools as my "stack" after going around the block a few times. But even so, I must recognise how awful the experience is for new users. It's taken me years to settle into this system, and it can take half a day to get someone up to speed with these tools if they haven't used them. I also work a lot…
I have issues precisely because of the misguided preference for virtualenvs in favor of traditional system package installation. It's obnoxious that pip now admonishes you for installing into site-packages even on a Debian system where that can't cause massive breakage. When you need isolated containers it's great. Everyone doesn't need a webdev focused, reproducible build for everyday shell life.
For individualised shell usage, sure. I have global installations of common data science utilities like pandas and jupyter, or requests.
Reproducibility isn't just about deployment, it's also about coordination with colleagues.