That being said, after two decades of using Python professionally, the only really problems I’ve ever encountered are “package doesn’t support this version for {reasons}” and “ML library is doing something undocumented and/or dumb with a specific Python version.” The former is normally because the package author is no longer their package and the latter is because, again, the ML community is among the absolute worst at creating solid tooling.
However, Python (1991) is only 2 yrs older than R (1993)
That's a vast exaggeration. It is not "really really" hard to spin up a venv and specify your requirements. People just don't do it, and blame the tools for what are bad engineering practices agnostic to any language.
"Really really" not easy would be handling C, C++, etc. dependencies.
I really really wish it was, as then I wouldn't have had to learn Docker.
Maybe more time than getting python deps to work but more deterministic and takes less cleverness.
Consider R, which is filled with the same kind of people. There's one package repository and if your package doesn't build cleanly under the latest version of R, it's removed from the repo.
Don't get me wrong, this has other problems but at least it means that all packages will work with a single language version.