For me virtualenv+requirements is good enough. The only feature of Poetry that I miss is the ability to create wheels without a setup.py. But I don't create wheels when writing backend code. So I only use Poetry for working with packages.
One gripe with pyproject.toml is that I can’t do editable installs (i.e ‘pip install -e path/to/package/‘) with it. Highly annoying when trying to patch packages.
[tool.poetry.dependencies] my-package = { "path" = "path/to/package", develop = true }
This way you can patch my-package and poetry will always install the latest state of it.
It cannot replace all setup.py use cases, but for pure python packages it can replace it completely.