Cargo is not hugely different from Maven which has been working fine for over a decade. Yes, it takes some polished ideas from other systems, but Python has had more packaging tools come and go than several other ecosystems put together.
+1 from Maven. And Maven was launched in 2004, 17 (!) years ago. It's almost old enough to vote.
A lot of ecosystems put on some solid horse blinders in order to avoid Java at all costs (Javascript/Node/NPM being another example). They've avoided good ideas from Java for more than a decade.
Migrating python2 -> python3 is hard because it requires rewriting code and because you can't really run python3 code if you depend upon python2.
If poetry create consume non-poetry packages and create packages which other package management systems can consume? If so, then:
1. Projects can move more effectively independently.
2. Projects can re-package as a single task rather than a massive rewrite effort.
Rust is incredibly lucky to have been created when it was because it benefits immensely from these things (I think it's the best new-to-middle-aged production-usable systems language out there today).
I agree with the idea but languages like Python and their ecosystems are really hard to move (remember python 2->3? is that even over?) -- it's a herculean and often impossible task.