I would consider both of those flaws of Rye, not Poetry. Python package managers not written in Python will by definition have less contributors, and to me, they make Python look like a toy language (you can't write a package manager, a fairly trivial program with the exception of dependency management, in Python - what can you write then?)

As for managing Pythons, I would consider this to be orthogonal to packaging, and the default system Python is often good enough.