Quoting the GitHub page[0]:
> PDM is meant to be a next generation Python package management tool. It was originally built for personal use. If you feel you are going well with Pipenv or Poetry and don't want to introduce another package manager, just stick to it. But if you are missing something that is not present in those tools, you can probably find some goodness in pdm.
Having used PDM a bit, its ambition in my opinion may not be to replace existing tools, but rather to experiment and implement the most recent PEPs related to packaging.
While you can argue about PEP 582[1] implementation (which is still in draft), PDM doesn't prevent anyone from using virtual environments, and even provides a plugin[2] to support that. PDM also implements PEP 631[3], which most other package managers have been relunctant to support or slow to adopt.
[0]: https://github.com/pdm-project/pdm
[1]: https://www.python.org/dev/peps/pep-0582/