>> This is due to the fact that not all libraries on PyPI have properly declared their metadata and, as such, they are not available via the PyPI JSON API. At this point, Poetry has no choice but downloading the packages and inspect them to get the necessary information. This is an expensive operation, both in bandwidth and time, which is why it seems this is a long process.

This sounds like something that could be done server side, either by PyPI or another entity and expose it through a new API endpoint, instead of doing it on every Python developer's machine.