If you are using system python only to create venvs you are fine. As soon as you install or start modifying the system python in anyway, you are on the path to ruin.
Debian is particularly bad because they'd comingle python 2 and 3 packages in the same filesystem locations if you used pip out of the box.
That was a horrid discovery on my part. I assumed, coming from java where this sort of thing has been a long solved problem, that no one would be daft enough to do something like that.
God save people who don't know you're 'supposed' to use something else.
Most projects state something like "run pip install whatever", which people will then do. If you're lucky, it will ask for sudo. If you're even luckier, you stop to think before entering your password.
Node has the exact same issue for people who globally install all packages. The only differences are A) python makes environment management the dev's choice/responsibility and B) defaults to system vs environmental.
I actually far prefer the Python method to, say, Go's GOPATH. But, I far prefer Rust/Cargo to either.
Sure, GOPATH really sucked, but that's why we got Go Modules. I don't think it's fair to compare Python to Go anymore.
I wish Python got a standard integrated solution for package management that works.
pip doesn't cut it in my book since it doesn't let you specify dependencies reproducibly. It either doesn't support lockfiles or ONLY supports having a lockfile, without dependencies.
venv also doesn't cut it since you have to remember to explicitly activate it and keep track of which venv is activated right now.
If we take a look at the much-maligned Node.js+npm, it's still far better than what built-in tools in Python let you have. Yes, Node.js doesn't provide full isolation from globally-installed node_modules, but at least it supports a local node_modules directory and lets it take preference. Notably Node.js+npm, with all its warts, doesn't suffer from the the two issues I've mentioned above.
I always use the system Python plus virtualenv and that works fine, it's certainly never broken my system...
I don't even know by what mechanism that breakage would happen.