Poetry gives you exactly what pip and venv give you, with the two pretty much perfectly integrated, in a way that is pleasant to use and not something that you'll grudgingly migrate your project to after your fifth dependency.

Well, poetry gives you a lock file, separation between dev dependencies and runtime dependencies, and easy deployments to PyPI. If you're hacking a oneof-script you might not need these features, but for "real" projects Poetry is invaluable.